title: The influence of plasma renin substrate on the relationship between plasma renin activity and plasma renin concentration. An experimental study in hyper- and hypothyroid rats.
abstract: The effects of endogenous Plasma Renin Substrate (PRS) on the relationship between Plasma Renin Activity (PRA) and the Plasma Renin Concentration (PRC) have been studied in hyperthyroid rats, by I-triiodothyronine (T3) administration and in hypothyroid rats, by propylthiouracil (PTU) treatment, to clarify if PRA changes are an adequate index for evaluating the renin-angiotensin changes during the alterations in the thyroid function. Although in experimental situations studied the induced variation on PRC explains a 62 per cent of the changes in PRA, finding a good lineal correlation between both parameters (r = 0.79, P less than 0.001). Not only does PRS play an important role on the kinetic of the enzymatic reaction but also explains jointly with PRC up to a 85 per cent of PRA alterations. PRS changes become more important during thyrotoxicosis where they limit in a higher degree the velocity of reaction due to inverse relationship between PRC and PRS (r = 0.74, P less than 0.001).
mesh_terms: D000808:Angiotensinogen / Q000097:blood*; D000809:Angiotensins / Q000097:blood*; D000818:Animals; D006980:Hyperthyroidism / Q000201:enzymology*; D007037:Hypothyroidism / Q000201:enzymology*; D008297:Male; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012083:Renin / Q000097:blood*; D012084:Renin-Angiotensin System / Q000187:drug effects
chemical_list: D000809:Angiotensins; D000808:Angiotensinogen; D011433:Propranolol; D012083:Renin