Renin in the blood plasma
The reference concentration of renin in blood plasma when it is collected in the horizontal position( lying) is 0.2-1.6 ng /( mL-h) of angiotensin I;when standing( standing) - 0,7-3,3 ng /( ml-h) angiotensin I.
Renin is a proteolytic enzyme secreted by a group of cells located in close proximity to the renal glomeruli( and therefore called the juxtaglomerular apparatus).Renin secretion in the kidneys is stimulated by a decrease in blood pressure in the arteries leading to the glomeruli, a decrease in the concentration of sodium in the area of the dense spot and distal tubules, and also as a result of activation of the sympathetic system. The most important factor, which enhances the formation of renin, is a decrease in renal blood flow. Reduced renal blood flow is often due to a general decrease in blood pressure. Renin released into the blood acts on angiotensinogen, resulting in a biologically inactive angiotensin I, which under the action of ACE undergoes further conversion to an-i-hiotensin II.ACE, on the one hand, catalyzes the conversion of angiotensin I into one of the most potent vasoconstrictors, angiotensin II, on the other hand, hydrolyses the bradykinin vasodilator to an inactive peptide. In this regard, drugs - ACE inhibitors are effective for lowering blood pressure in patients with renal arterial hypertension.
To evaluate the results of renin plasma research, only stimulated indicators are most significant( for example, after stimulation with furosemide).When determining the level of renin, stimulated by furosemide, it is necessary to simultaneously determine the sodium and creatinine in daily urine and potassium, sodium and creatinine in the blood. To diagnose arterial hypertension associated with stenosis of the renal arteries or lesion of the parenchyma of one kidney, the activity of renin in the blood taken directly from both renal veins is examined. If the absolute activity of renin in the blood from the renal veins is increased or the renin activity from the vein of the affected kidney is more than 1.5 times greater than the renin activity on the healthy side, it is possible to state with certainty renal artery stenosis that disrupts the kidney function.
Very high values of renin activity in the blood are observed with reninomas. The activity of renin in the blood gradually decreases with age.
The main diseases and conditions in which the renin activity in the blood plasma can change are presented in Table. .
Table Diseases and conditions in which the renin activity in the blood plasma can vary