Connexin 43 is not essential for the control of renin synthesis and secretion

The juxtaglomerular areas of mammalian kidneys express the gap junction proteins connexin 37, 40, 43, and 45. Among these, Cx40 plays a major role for the function of juxtaglomerular renin-expressing cells, while Cx37 and Cx45 appear to be less relevant in this context. Since the role of the remaining Cx43 for the function of renin expression is not well understood, this study aimed to systematically characterize the direct role of Cx43 for renin expression and secretion. For this aim, we generated mice with endothelium and with renin cell-specific deletions of Cx43, and we characterized the regulation of renin expression and renin secretion in the kidneys of these mice on normal salt diet and during chronic challenge of the renin system by pretreatment of mice with a low-salt diet in combination with an angiotensin I-converting enzyme inhibitor. We found that renal renin mRNA abundance, plasma renin concentration, and systolic blood pressure did not differ between wild-type, Cx43(fl/fl) Ren1d(+/Cre) mice as well as Cx43(fl/fl) Tie-2(+/Cre) mice under basal conditions nor under chronic stimulation by salt depletion. The localization of renin-expressing cells was also regular in kidneys of all genotypes, and moreover, regulation of renin secretion by beta-adrenergic stimulation and renal perfusion pressure measured in isolated perfused kidneys of Cx43(fl/fl) Ren1d(+/Cre) and Cx43(fl/fl) Tie-2(+/Cre) mice was not different from control. We infer from these results that Cx43 plays if at all only a minor role for the functional control of renin-producing cells in the kidney.