AJP - Endocrinology and Metabolism, Vol 239, Issue 6 396-E400, Copyright © 1980 by American Physiological Society
Regulation of renal adenylate cyclase by parathyroid hormone
D. L. Carnes, G. A. Nickols, C. S. Anast and L. R. Forte
This study reports the effects of the removal of endogenous PTH by
thyroparathyroidectomy (TPTX) on the recovery of the reduced renal cAMP
response to parathyroid hormone (PTH) in rats with chronically elevated PTH
secondary to diets deficient in either vitamin D or calcium. After TPTX and
infusion with a calcium-glucose solution of the vitamin D-deficient rat,
calcium and PTH fell from 5.8 mg/dl and 2,509 pg/ml, respectively, to 4.8
mg/dl and 160 pg/ml at 48 h. There was a partial restoration of response to
PTH, assessed by assay of renal cortical adenylate cyclase activity from
64% of control activity prior to TPTX to 84% of control activity at 48 h.
When rats fed the diet deficient in calcium were TPTX, serum PTH fell
rapidly from 2,811 to 200 pg/ml at 5 h with no further change at 21 h,
whereas calcium did not change (5.3 mg/dl). PTH-dependent adenylate cyclase
activity increased from 59% of control activity prior to TPTX to 87% at 5 h
and 100% of control activity at 21 h after TPTX. Each diet produced similar
increases in the serum level of immunoreactive PTH, and the rate of
disappearance of the circulating hormone after TPTX was also similar for
both groups of rats. The data indicate a slow, partial recovery of the
enzyme response to PTH after TPTX of the vitamin D-deficient rat over the
time period studied, whereas the recovery was rapid and complete in rats
fed the diet deficient in calcium.
