C-peptide stimulates Na+,K+-ATPase activity via PKC alpha in rat medullary thick ascending limb.

Aims/hypothesis: C-peptide, the cleavage product of proinsulin processing exerts physiological effects including stimulation of Na(+),K(+)-ATPase in erythrocytes and renal proximal tubules. This study was undertaken to assess the physiological effects of connecting peptide on Na(+),K(+)-ATPase activity in the medullary thick ascending limb of Henle's loop.

Methods: Na(+),K(+)-ATPase activity was measured as the ouabain-sensitive generation of (32)Pi from gamma[(32)P]-ATP and (86)Rb uptake on isolated rat medullary thick ascending limbs.

Cellular localization of type 5 and type 6 ACs in collecting duct and regulation of cAMP synthesis.

The cellular distribution of Ca(2+)-inhibitable adenylyl cyclase (AC) type 5 and type 6 mRNAs in rat outer medullary collecting duct (OMCD) was performed by in situ hybridization. Kidney sections were also stained with specific antibodies against either collecting duct intercalated cells or principal cells. The localization of type 5 AC in H(+)-ATPase-, but not aquaporin-3-, positive cells demonstrated that type 5 AC mRNA is expressed only in intercalated cells.

Functional properties of Ca2+-inhibitable type 5 and type 6 adenylyl cyclases and role of Ca2+ increase in the inhibition of intracellular cAMP content.

Among the different adenylyl cyclase (AC) isoforms, type 5 and type 6 constitute a subfamily which has the remarkable property of being inhibited by submicromolar Ca2+ concentrations in addition to Galphai-mediated processes. These independent and cumulative negative regulations are associated to a low basal enzymatic activity which can be strongly activated by Galphas-mediated interactions or forskolin. These properties ensure possible wide changes of cAMP synthesis.

[Regulation of intracellular cAMP content in kidney tubules: role of adenylyl cyclases inhibitable by calcium].

Adenylyl cyclase (AC) isoforms 5 and 6 can be inhibited by submicromolar concentrations of Ca2+. Quantitative RT-PCR allowed to study the corresponding messengers (mRNA) along the rat nephron. The results demonstrate a significant expression of AC 6 mRNA all along the nephron and of AC 5 mRNA in the glomerulus and the collecting tubule located in the cortex and the outer medulla.

Cell-specific coupling of PGE2 to different transduction pathways in arginine vasopressin- and glucagon-sensitive segments of the rat renal tubule.

1. The aim of the present study was to investigate the transduction pathways elicited by prostaglandin E2 (PGE2) to inhibit hormone-stimulated adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation in the outer medullary collecting duct (OMCD) and medullary thick ascending limb (MTAL) microdissected from the rat nephron. 2.