Nephron Distribution of Total Low Km Cyclic AMP Phosphodiesterase in Mouse, Rat and Rabbit Kidney.

Abstract

The activity of cAMP degradation enzyme, cAMP phosphodiesterase (cAMP PDE), in renal tubules is a critically important factor in determining cellular cAMP levels, particularly in response to hormones. In this study we examine the nephron distribution of cAMP PDE activity in the mouse, rat and rabbit kidney and important cellular regulators of cAMP PDE, namely calmodulin and adenosine triphosphate (ATP). We assayed total low Km cAMP PDE in microdissected tubule segments, using 10(-6) M (3H) cAMP as a substrate. Activities were expressed in fentomol cAMP hydrolyzed per minute per mm tubular length or per one glomerulus. The content of ATP was measured in outer medullary collecting duct and medullary thick ascending limb of Henle's loop with microbioluminescence assay using firefly luciferase. In mouse kidney, cAMP PDE was significantly higher in all tubular segments compared to glomerulus. Proximal convoluted tubule, proximal straight tubule, medullary thick ascending limb of Henle's loop (mTAL), and outer medullary collecting duct (OMCD) had intermediated activity. Greater cAMP PDE activity was detected in cortical ascending limb of Henle's loop (cTAL), cortical collecting duct and in distal convoluted tubule (DCT). The highest activity was found in connecting tubules. In rat, nephron distribution of cAMP PDE activities was similar to mouse, except that activity in glomeruli was higher than in mouse glomeruli. In rabbit, nephron distribution of cAMP PDE activities was different from those of mouse and rat. There was no single prominent segment with high cAMP PDE activity. DCT and cTAL showed low enzyme activity. Overall, the highest cAMP PDE activities were measured in the mouse and the lowest were measured in the rabbit nephrons, with those of rat nephron showing an intermediate activity. The maximum effective dose of the calmodulin antagonist, trifluoperazine (200 microM), inhibited cAMP PDE in all nephron segments from the rat kidney. However, there is no statistical significance of its inhibition among nephron segments. In OMCD and mTAL of the rat kidney, cAMP PDE activity was inhibited by ATP (5 mM to approximately 10 mM) which is far beyond the physiological concentartion of ATP in normal epithelial cell. Actual determinations of ATP in mTAL and OMCD were 0.1 mM and 0.17 mM, respectively. These observations show that distal segments of tubules have more active catabolism of cAMP than proximal segments. cAMP PDE in each nephron segment appear to be almost equally dependent on trifluoperazine-sensitive pathway that may reflect the Ca2+-calmodulin system. Cellular concentration of ATP might not be involved in the regulation of the total low Km cAMP PDE activity in rat mTAL and OMCD.

Effects of hydration in rats and mice with polycystic kidney disease

“…The renal phenotype of Pkd1 or Pkd2 heterozygous knockout mice is similarly normal or very mild; unfortunately, no Pkd1 or Pkd2 rat model currently exists (21). Furthermore, in previous studies, we and others (12,27) reported higher PDE activities in kidneys from mice compared with those from rats. Since the hydrolytic capacity of PDEs far exceeds the maximum rate of synthesis by adenylyl cyclases, cellular levels of cAMP may be more sensitive to changes in PDEs compared with those in adenylyl cyclases.…”

Calmodulin Is Required for Vasopressin-stimulated Increase in Cyclic AMP Production in Inner Medullary Collecting Duct

“…Given the multiplicity of its actions in cells, calmodulin likely plays other physiologically significant roles in the IMCD. One such role is stimulation of phosphodiesterase activity, which has been demonstrated in prior studies (49,50). The potential attenuation of the cAMP response via CaM-sensitive phosphodiesterase-1 has not been addressed in this study.…”

Modulation of Polycystic Kidney Disease Severity by Phosphodiesterase 1 and 3 Subfamilies

“…14,15 PDE1 accounts for most of the PDE activity in renal tubules 16,17 and is the only PDE activated by calcium 14,15 (which is reduced in PKD cells), and its activity is reduced in cystic kidneys. 17 Furthermore, the pool of cAMP generated in response to vasopressin (the main adenylyl cyclase agonist in collecting duct and distal nephron 18 ) is mainly hydrolyzed by PDE1, and the accumulation of cAMP in response to vasopressin is markedly increased when intracellular calcium is reduced, mainly because of lower PDE1 activity.…”

“…35 A possible explanation for the different susceptibility of mice and rats to the development of PKD and the cystogenic effects of DDAVP could be the higher PDE activities reported in kidneys from mice compared with those from rats. 16,17 To test this hypothesis, we administered DDAVP (30 ng/100 g body wt per hour subcutaneously using a osmotic minipump) to and Pkd2 2 /WS25 ;Pde3b 2 /2 mice had slightly higher body and liver weights but no increase in liver cystic or fibrotic indices. These results are consistent with the hypothesis that PDE3 activity limits the cystogenic effect of DDAVP in mouse models of PKD.…”