Ontogeny of renal renin in congenital hypothyroid rats

in the present study we have found age-related differences between the rena l renin activity (RPA) and the immunoreactive renal renin (IRR) profiles du ring the neonatal development of the rat. RRA was markedly greater in newbo rn rats than in adult ones, while IRR was low at birth and progressively in creased until adulthood. These observations suggest the existence of a cont rol mechanism operating either at the level of the translation of the templ ate or at a post-translational level which varies thronghout the developmen t. Since thyroid hormones have been demonstrated to affect several renin-an giotensin components, the neonatal RRA and IRR profiles in congenital hypot hyroid rats were evaluated to determine whether renal renin activity or its synthesis could be endogenously regulated by thyroid hormones in the early stages of life. Although significant differences were observed in the RRA profiles of congenital hypothyroid and control rats, no changes were found in the relative amount of immunoreactive protein. These findings indicate t hat thyroid hormone deficiency does not directly affect renal renin express ion during the critical period of the normal morpho-functional development of the newborn.