Effects of parathyroid hormone and calcitonin on stop-flow patterns of cyclic AMP, sodium, potassium, calcium and inorganic phosphate in thyroparathyroidectomized rabbits.
Conventional stop-flow studies were performed in thyroparathyroidectomized rabbits in order to examine the effects of parathyroid hormone (PTH) and calcitonin on urinary excretion of 3',5'-cyclic adenosine monophosphate (cAMP), Na, K, Ca, and inorganic phosphate (Pi). PTH markedly increased excretion of cAMP in the distal as well as in the proximal fractions. PTH increased Na concentration at the proximal and the distal fractions. K concentration was increased with PTH in all segments, and two prominent peaks were observed at the late proximal and the terminal fractions. Although changes in the pattern of Ca concentration after PTH were similar to those of Na, the pattern of Ca concentration normalized by Na concentration (Ca/Na) showed a decrease in Ca concentration in the late distal fractions. PTH increased Pi concentration in two portions, the proximal and the late distal fractions. Calcitonin slightly increased excretion of cAMP at the midfractions. Calcitonin did not cause any significant changes in the patterns of Na and Pi, but increased Ca concentration in the early distal fractions and K concentration in the late proximal fractions. From these findings we suggest: (a) nephrogenous cAMP responsive to each hormone partly corresponds to nephron distribution of hormone-dependent adenylate cyclase; (b) the sites of action of these hormones are quite distinct in the rabbit kidney; (c) the distal nephron segments play important roles in anticalciuric and phosphaturic actions of PTH, and (d) mechanisms of increases in K excretion by these two hormones may be different.
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002116:Calcitonin / Q000494:pharmacology*; D002118:Calcium / Q000652:urine; D000242:Cyclic AMP / Q000652:urine; D005260:Female; D008297:Male; D009399:Nephrons / Q000187:drug effects* / Q000201:enzymology; D010280:Parathyroid Glands / Q000502:physiology; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010710:Phosphates / Q000652:urine; D011188:Potassium / Q000652:urine; D011817:Rabbits; D012964:Sodium / Q000652:urine; D013961:Thyroid Gland / Q000502:physiology
D010281:Parathyroid Hormone; D010710:Phosphates; D002116:Calcitonin; D012964:Sodium; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D011188:Potassium; D002118:Calcium