Effect of parathormone and cyclic adenosine monophosphate on renal bicarbonate reabsorption.

KARLINSKY,MALCOLM L., DAVID S. SAGER,NEIL A. KURTZMAN, AND V. K. G. PILLAY. Efect of parathormona and cych adenosine monophosphate on wnal bicarbonate reabsorption. Am. J. Physiol. 227(6): 12264231. 1974.-Several recent studies have suggested that parathyroid hormone directly depresses renal bicarbonate reabsorptionTo test this thesis, we infused highly purified parathyroid hormone (PTH) and dibutyryl cyclic adenosine monophosphate (CAMP) to bicarbonate-loaded dogs. Identical infusions were given to nonloaded dogs. These agents caused a marked phosphaturia in the nonloaded animals and a transient increase in bicarbonate excretion which achieved statistical significance in the case of CAMP. PTH depressed bicarbonate reabsorption ; I I however, the rate of bicarbonate reabsorption seen in these PTH-treated animals was not different from that seen in animals not receiving PTH, but otherwise identically treated. Bicarbonate reabsorption was also measured in thyroparathyroidectomized dogs. Bicarbonate reabsorption was found to be elevated in these animals to 30-32 meq/liter GFR; infusion of either CAMP or PTH dropped bicarbonate reabsorption to the %ormal” value of about 24 meq/liter GFR. These studies demonstrate a major regulatory role of PTH over renal bicarbonate reabsorption, but do not show that PTH administration will depress bicarbonate reabsorption to a level low enough to result in metabolic acidosis.