In vitro methods are useful for screening potential antihypertensive drugs. Enzyme inhibition assays can identify ACE inhibitors that block the RAAS pathway. Ion channel assays can find calcium channel blockers. Receptor binding assays have found angiotensin receptor blockers. These targeted in vitro assays help develop more effective antihypertensive drugs, though in vivo testing is still needed to confirm efficacy and safety.

2. INTRODUCTION
Hypertension is a chronic medical condition characterized by elevated blood pressure levels in the arteries.
Blood pressure is a measure of the force of blood against the walls of arteries as the heart pumps it throughout the body.
Hypertension is defined as blood pressure reading of 140/90 mmHg or higher, and it affects nearly one-third of the adult population worldwide.
Hypertension is a major risk factor for cardiovascular disease, including conditions such as heart disease, stroke, and heart failure.
Uncontrolled hypertension can lead to damage to blood vessels and organs, including the heart, kidneys, and brain, which can increase the risk of
developing serious health problems such as heart attacks, strokes, and kidney failure.
Managing hypertension is critical in preventing cardiovascular disease and related complications.
Treatment of hypertension typically involves a combination of lifestyle modifications and medications, with the goal of reducing blood pressure to a
normal or near-normal range.
Lifestyle modifications may include weight loss, regular exercise, a healthy diet, limiting alcohol consumption, and reducing stress.
In some cases, medication may be required to achieve optimal blood pressure control.
Hypertension management has been shown to significantly reduce the risk of cardiovascular events, including heart attacks and strokes.
Controlling hypertension can also slow the progression of other conditions, such as kidney disease and diabetes, that are often associated with
hypertension.

3. PATHOPHYSIOLOGY
Hypertension is a complex condition with multiple underlying mechanisms, including increased vascular resistance, arterial stiffness,
vasoconstriction, and endothelial dysfunction.
The renin-angiotensin-aldosterone system (RAAS) plays a key role in regulating blood pressure.
Renin is released from the kidneys in response to decreased blood pressure, which catalyzes the conversion of angiotensinogen to angiotensin I.
Angiotensin I is converted to angiotensin II by the angiotensin converting enzyme (ACE) in the lungs.
Angiotensin II is a potent vasoconstrictor and also stimulates the release of aldosterone, which promotes sodium and water retention.
Sympathetic nervous system activation can also contribute to hypertension by increasing heart rate and causing vasoconstriction.
Abnormalities in the production and metabolism of vasoactive substances such as nitric oxide and endothelin can also contribute to hypertension.
Understanding the mechanisms underlying hypertension is crucial for developing effective antihypertensive drugs.
Antihypertensive drug classes include ACE inhibitors, angiotensin receptor blockers, calcium channel blockers, diuretics, and beta blockers.
These drugs target different aspects of the pathophysiology of hypertension, such as decreasing vascular resistance, blocking the effects of
angiotensin II, reducing sympathetic nervous system activity, or promoting sodium and water excretion.

4. LIST OF ANIMAL MODELS
Spontaneously hypertensive rats (SHR) model
Renovascular hypertensive models
Transgenic animal models
Angiotensin II-infused models
DOCA-salt hypertensive models
Two-kidney, one-clip (2K1C) model
Goldblatt 2-kidney, 1-clip (2K1C) hypertension model
Obese hypertensive animal models
Dahl salt-sensitive rat model
Renin-transgenic hypertension model

5. SPONTANEOUSLY HYPERTENSIVE RATS (SHR]
MODEL
Spontaneously hypertensive rats (SHR) are a widely used animal model for studying hypertension and evaluating
potential antihypertensive drugs.
SHR are an inbred strain of rats that were selectively bred for their genetic predisposition to develop hypertension,
making them a useful model for investigating the mechanisms underlying essential hypertension in humans.
SHR exhibit many of the same characteristics of human hypertension, including elevated blood pressure, cardiac
hypertrophy, and increased vascular resistance.
The SHR model has been extensively used to study the pathophysiology of hypertension, including the role of the renin-
angiotensin-aldosterone system and other neurohumoral factors.
SHR are commonly used to evaluate the efficacy and safety of potential antihypertensive drugs by administering the
drug to SHR and monitoring their blood pressure and other cardiovascular parameters over time.
One advantage of the SHR model is that it is relatively easy and cost-effective to use, as they are widely available and
have been extensively characterized.
However, the use of SHR is limited by its inbred nature, which limits genetic variability, and the fact that it may not fully
recapitulate the complex pathophysiology of human hypertension.
Overall, the SHR model is a valuable tool for investigating hypertension, but it should be used in conjunction with other
animal models and clinical studies to ensure that the findings are relevant to human disease.

6. RENOVASCULAR HYPERTENSIVE MODELS
Renovascular hypertensive models involve inducing hypertension by restricting blood flow to
the kidneys.
Two commonly used models are the two-kidney, one-clip (2K1C) model and the one-kidney,
one-clip (1K1C) model.
The 2K1C model involves placing a silver clip around one renal artery, which results in
reduced blood flow to that kidney and activation of the renin-angiotensin-aldosterone system.
The 1K1C model involves placing a silver clip around the renal artery of the only functioning
kidney in the animal.
Renovascular hypertensive models can mimic human renovascular hypertension, which is a
common cause of secondary hypertension.
These models are relatively easy to induce and have consistent blood pressure responses,
making them useful for drug screening studies.

7. LIMITATIONS
However,
these
models
have
limitations:
They can be invasive and require surgical
procedures, which can be stressful for the
animals and increase the risk of
complications.
They do not fully replicate the complex
pathophysiology of human hypertension,
as they do not account for factors such as
obesity, aging, and other comorbidities.

8. ANGIOTENSIN II-INFUSED MODELS
Angiotensin II-infused models involve administration of angiotensin II to animals to induce hypertension.
Angiotensin II is a potent vasoconstrictor and plays a central role in the renin-angiotensin-aldosterone system (RAAS).
The model is commonly used in drug screening due to its quick and reliable induction of hypertension.
Angiotensin II can be infused subcutaneously or intravenously, leading to an increase in blood pressure within a few
days.
The model exhibits pathophysiological features similar to human hypertension, such as increased vascular resistance
and inflammation.
Limitations include that it does not reflect the chronic nature of hypertension and does not involve the complex
interactions between different systems in the body.
High doses of angiotensin II can lead to non-specific effects and toxicity.
This model can be useful for identifying potential antihypertensive agents that target the RAAS pathway.
However, it should be complemented with other animal models to fully understand the efficacy and safety of the drugs

9. TRANSGENIC ANIMAL MODELS
Transgenic animal models involve the insertion or deletion of genes in the animal's DNA to study the effects of
specific genes on disease development and progression.
Ren-2 and TGR(mRen2)27 rats are commonly used transgenic animal models for hypertension research.
Ren-2 rats overexpress the renin gene and develop hypertension, while TGR(mRen2)27 rats express a
mutant human renin gene and develop severe hypertension and cardiac hypertrophy.
Advantages of transgenic animal models include the ability to study the effects of specific genes on disease
development and evaluate the efficacy of drugs targeting those genes.
Limitations of transgenic animal models include the high cost and technical expertise required to create and
maintain these models, potential off-target effects, and species differences in gene regulation and physiology.
Findings in transgenic animal models may have limited relevance to humans, and should be used in
conjunction with other animal models and clinical studies to ensure the relevance of the findings.

10. DOCA-SALT HYPERTENSIVE MODEL
DOCA-salt hypertensive model involves administration of DOCA and high salt diet to
induce hypertension in animals.
The model mimics human hypertension in terms of pathophysiology and clinical
features.
DOCA causes sodium retention and potassium loss, leading to salt retention and
elevated blood pressure.
High salt diet exacerbates the effect by increasing sodium intake and elevating blood
pressure further.
Advantages of using DOCA-salt model include its ability to closely mimic human
hypertension and high success rate in inducing hypertension.
DOCA-salt model is a useful tool for testing the efficacy and safety of antihypertensive
drugs.
Limitations of the model include potential kidney damage and limited applicability in
certain contexts due to not accounting for other factors such as genetics and lifestyle.

11. THE 2K1C MODEL IS
The 2K1C model is an animal model of renovascular hypertension
It involves the surgical placement of a clip on one of the renal arteries
This leads to decreased renal perfusion and activation of the renin-angiotensin-aldosterone system (RAAS)
Resulting in the development of hypertension and renal damage
The 2K1C model mimics the pathophysiology of human renovascular hypertension
It allows for the evaluation of drugs that target the RAAS
The model has been used to study the mechanisms underlying hypertension-induced renal damage
The model can be used to evaluate the efficacy of interventions to prevent or reverse renal damage
One advantage of the 2K1C model is that it induces a stable and predictable form of hypertension, making it useful for long-term studies of drug
effects
Limitations of the model include variability in the degree of hypertension induced by the clip
The potential for the development of compensatory mechanisms that can mask the effects of interventions

12. THE GOLDBLATT 2-KIDNEY, 1-CLIP (2K1C)
HYPERTENSION MODEL
The Goldblatt 2-kidney, 1-clip (2K1C) hypertension model is an animal model for screening
antihypertensive drugs.
This model involves the placement of a silver clip around one of the renal arteries, leading to reduced
blood flow and hypertension.
The 2K1C model is named after Harry Goldblatt, who first described it in 1934.
This model is commonly used to study the effects of drugs that target the renin-angiotensin-
aldosterone system, such as ACE inhibitors and angiotensin receptor blockers.
The 2K1C model reproduces many features of human hypertension, including increased vascular
resistance, elevated blood pressure, and renal dysfunction.
However, the 2K1C model has limitations, such as variability in the response to drug treatments
among different animals and not always replicating the progression of human hypertension.
Nonetheless, the 2K1C model remains a valuable tool for investigating the mechanisms of
hypertension and developing new antihypertensive drugs.

13. OBESE HYPERTENSIVE ANIMAL MODELS
Obese hypertensive animal models are animals that are genetically modified or induced to develop both
obesity and hypertension.
Obesity and hypertension are closely related, as obesity is one of the risk factors for developing hypertension.
Obese hypertensive animal models can be induced through various methods, such as feeding animals with a
high-fat diet or inducing genetic modifications that lead to the development of obesity and hypertension.
One commonly used obese hypertensive animal model is the obese Zucker rat, which develops both obesity
and hypertension due to a defect in the leptin receptor.
Other examples of obese hypertensive animal models include the spontaneously hypertensive obese rat and
the diet-induced obese rat.
Using obese hypertensive animal models for drug screening can provide insights into the interactions between
obesity and hypertension and help develop drugs that target both conditions.
However, these models also have limitations, such as the complexity of the interactions between obesity and
hypertension and the difficulty of accurately modeling human obesity and hypertension in animals.

14. THE DAHL SALT-SENSITIVE RAT MODEL
The Dahl salt-sensitive rat model is commonly used for studying
hypertension
These rats are genetically predisposed to develop hypertension in
response to a high salt diet
When fed a high salt diet, they develop hypertension and renal injury
similar to what is observed in humans
Useful in studying the pathophysiology of salt-sensitive hypertension and
evaluating potential antihypertensive drugs
Limitations include high sensitivity to variations in diet and environment,
which can affect consistency and reproducibility of results

15. RENIN-TRANSGENIC HYPERTENSION MODEL
Renin-transgenic hypertension model is a transgenic animal model in
which the overexpression of the renin gene leads to hypertension.
Renin is a hormone that plays a crucial role in regulating blood pressure
by catalyzing the conversion of angiotensinogen to angiotensin I, which
is further converted to angiotensin II, a potent vasoconstrictor.
In this model, the renin gene is overexpressed in specific tissues or
organs, leading to increased levels of circulating renin and subsequent
activation of the renin-angiotensin-aldosterone system.
The renin-transgenic model has been used to study the mechanisms
underlying hypertension and to test the efficacy of antihypertensive
drugs that target the renin-angiotensin-aldosterone system.

16. ADVANTAGES AND LIMITATIONS
Advantages
of this
model:
Allows for the selective overexpression of the renin gene in
specific tissues or organs, which can help researchers better
understand the role of renin in hypertension.
Limitations
of this
model:
May not accurately reflect the complex mechanisms involved in
hypertension in humans.
Highly specific and artificial model of hypertension.
Use of transgenic animals may raise ethical concerns and may
not be a feasible option for all researchers.

17. In vitro methods for drug screening involve testing compounds in a laboratory setting using isolated cells, tissues, or organs.
These methods are often used in the early stages of drug discovery to identify potential drug candidates and to assess their efficacy
and safety.
High-throughput screening is an example of in vitro methods for antihypertensive drug screening that involves testing large numbers
of compounds using automated systems to rapidly identify those with the desired activity.
Receptor binding assays can be used to identify compounds that interact with specific receptors involved in hypertension, such as
the angiotensin receptor.
Enzyme inhibition assays and ion channel assays can also be used to identify compounds that modulate enzymes or ion channels
involved in hypertension.
Receptor binding assays involve the use of radiolabeled ligands to measure the binding affinity of a drug candidate to a specific
receptor.
Angiotensin II is a potent vasoconstrictor that binds to the angiotensin II receptor, leading to increased blood pressure.
Drugs that target the RAAS, such as angiotensin receptor blockers (ARBs), have become a mainstay in the treatment of
hypertension.
Receptor binding assays can be used to identify potential ARBs or other compounds that interact with the angiotensin receptor.
Compounds with high binding affinity are considered potential ARBs and can be further evaluated in in vivo models for efficacy and
safety.

18. In vitro methods involve testing compounds in a laboratory setting using isolated cells, tissues, or organs to identify
potential drug candidates and assess their efficacy and safety.
Examples of in vitro methods for antihypertensive drug screening include high-throughput screening, receptor binding
assays, enzyme inhibition assays, and ion channel assays.
Enzyme inhibition assays measure the ability of a compound to inhibit the activity of a target enzyme involved in
hypertension.
ACE inhibitors, a common class of antihypertensive drugs, work by inhibiting the activity of ACE, an enzyme involved in
the renin-angiotensin-aldosterone system.
Ion channel assays measure the ability of a compound to modulate the activity of ion channels involved in hypertension.
Calcium channel blockers, another common class of antihypertensive drugs, work by blocking the activity of calcium
channels in cardiac and smooth muscle cells.
Receptor binding assays can be used to identify potential angiotensin receptor blockers (ARBs) or other compounds
that interact with the angiotensin receptor, a key component of the renin-angiotensin-aldosterone system.
In vitro methods are powerful tools for identifying potential antihypertensive compounds with specific activity against
targets involved in hypertension, allowing for the development of more targeted and effective antihypertensive drugs.

19. IN VITRO METHODS
Enzyme Inhibition Assays:
Enzymes play a crucial role in many physiological processes, including blood pressure regulation
Enzyme inhibition assays are commonly used to identify compounds that modulate enzyme activity
ACE inhibitors are a common class of antihypertensive drugs that work by inhibiting the activity of ACE, an enzyme involved in the renin-angiotensin-aldosterone system
Enzyme inhibition assays can be used to identify compounds that inhibit ACE activity or the activity of other enzymes involved in hypertension
Ion Channel Assays:
Ion channels play a crucial role in regulating the electrical activity of cells, including cardiac and smooth muscle cells
By modulating ion channel activity, it is possible to affect blood pressure regulation
Calcium channel blockers are another common class of antihypertensive drugs that work by blocking the activity of calcium channels in cardiac and smooth muscle cells
Ion channel assays can be used to identify compounds that modulate the activity of calcium channels or other ion channels involved in hypertension
Benefits:
These assays can identify compounds with specific activity against targets involved in hypertension
This allows for the development of more targeted and effective antihypertensive drugs
Limitations:
In vitro assays may not accurately reflect the complex interactions that occur in vivo
Further testing in animal models and clinical trials is necessary to confirm the efficacy and safety of potential antihypertensive compounds.