Activation of rat plasma renin

Area of Science:

• Biochemistry
• Physiology
• Endocrinology

Background:

• Plasma renin exists in multiple molecular weight forms, including active and inactive (prorenin) species.
• Renin plays a crucial role in regulating blood pressure through the renin-angiotensin-aldosterone system.

Purpose of the Study:

• To investigate the different molecular weight forms of active renin in rat plasma.
• To elucidate the mechanism of renin activation, particularly the role of acid dialysis and endogenous factors.

Main Methods:

• Analysis of plasma renin molecular weight species using gel filtration chromatography.
• In vivo renin stimulation via anesthesia and hemorrhage.
• Acid dialysis of plasma at different pH levels (3.3 and 1.5) to assess renin activation and identify activating factors.

Main Results:

• Three active renin species (>150,000, 65,000, and 43,000 Da) were identified in conscious rats.
• Acute stimulation primarily detected the low molecular weight (43,000 Da) renin form.
• Acid dialysis (pH 3.3) increased total renin concentration, confirming the presence of inactive renin (prorenin), and shifted the proportion towards the 43,000 Da form.
• A renin- and substrate-free factor generated by pH 1.5 dialysis activated renin in normal plasma at pH 7.4, indicating an endogenous activator.

Conclusions:

• Rat plasma contains distinct active renin molecular weight forms, with the low molecular weight form predominating under stimulation.
• Acid dialysis activates prorenin not solely due to acidity but through an endogenous plasma factor.
• This study confirms the existence of an endogenous factor capable of converting inactive renin to active renin following acid treatment.