AJP - Renal Physiology, Vol 250, Issue 5 942-F948, Copyright © 1986 by American Physiological Society
Possible role of calcium in parathyroid hormone actions in rabbit renal proximal tubules
N. Yanagawa and O. D. Jo
Using a glucose microassay and in vitro isolated renal tubule perfusion
technique, we have studied the actions of parathyroid hormone (PTH) on
gluconeogenesis (GNG) and fluid (Jv) and phosphate (Jp) transport rates in
isolated rabbit renal proximal tubules. In proximal straight tubules (PST),
PTH stimulated GNG and inhibited Jv and Jp. In proximal convoluted tubules
(PCT), PTH inhibited Jv but failed to affect GNG and Jp. An increase in Ca
concentration, however, stimulated GNG and allowed PTH to inhibit Jp in
PCT. Addition of the intracellular Ca antagonists trifluoperazine and
N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) abolished the
inhibitory effects of PTH on Jv and Jp in both PCT and PST. In conclusion,
these studies suggest that Ca-dependent intracellular pathways may be
involved in the actions of PTH in rabbit renal proximal tubules. The
altered response to PTH in rabbit PCT may be due to alterations in the
response of intracellular Ca to the hormone.
