Changes in Glomerular and Cortical Tubular cAMP Metabolism in Kidneys from Rats with Unilateral Ureteral Obstruction

Abstract

Obstructive uropathy is associated with changes in several renal functions. As some of these are mediated by cAMP, we examined whether changes in cAMP metabolism could contribute to the pathophysiology of unilateral ureteral ligation in rats. We found that basal adenylate cyclase in the cortex of the obstructed kidney doubled after 3-7 days, but the response to NaF and parathyroid hormone was decreased. Similarly, in vivo infusion of parathyroid hormone resulted in lower cAMP levels in the cortex of the obstructed kidney. Parathyroidectomy or pretreatment with beta-adrenergic blocker had no effect. Prostaglandin inhibition by indomethacin decreased, but did not abolish, the differences.On the other hand, basal adenylate cyclase in glomeruli from contralateral kidneys was higher. Pretreatment with indomethacin reduced the basal activity in contralateral glomeruli, and led to increased degrees of stimulation with parathyroid hormone and prostaglandins.Furthermore, we demonstrated that isolated glomeruli contain cAMP-dependent protein kinase that is found predominantly in the 30,000 g supernatant fraction and that by DEAE-cellulose chromatography has the characteristics of a type II kinase. In glomeruli from rats with unilateral ureteral ligation, the distribution and degree of activation of the cAMP-dependent protein kinase are affected differently on the ligated and contralateral sides, probably reflecting the change in glomerular cAMP generation.These results indicate that changes in cAMP metabolism may contribute to the altered cortical tubular function in unilateral ureteral ligation and may be partially related to enhanced prostaglandin synthesis in the obstructed kidney. On the other hand, the higher adenylate cyclase activity and the change in cAMP-dependent protein kinase activity in glomeruli from the contralateral kidney may in part reflect increased PGE2 production by these glomeruli. The results support the concept that similar to their in vitro action, locally generated prostaglandins may in vivo affect cortical tubular function by influencing the tubular cAMP system while those generated in the glomerulus alter glomerular cAMP metabolism.