Isolated glomeruli in vitro: an approach to the macula-densa-mediated renin release.
The introduction of an assay for adenylate kinase into the study of renin release from isolated glomeruli is a useful tool in determining the specificity of the release process. Interestingly, even the absolute values of AK activity yield information that might be of value in understanding the effects on net renin output in media of grossly unphysiological composition. In qualitative terms, though, the AK measurements provide evidence against an unspecific loss of cytoplasmatic proteins as the cause of increased release of renin after removal of calcium or sodium bicarbonate. This renin release must have come from a compartment other than the cytoplasma of the juxtaglomerular cells. The in vivo position of the juxtaglomerular cells remaining in the present preparation, situated at the polkissen only few microns from the only hypoosmotic area in the body, suggests that the extreme osmosensitivity of renin release from isolated glomeruli represents a physiologic phenomenon. Because urea and sodium chloride are the predominant solutes in the tubular fluid at the macula densa, available data from isolated glomeruli are consistent with a macula densa feedback mechanism if it is accepted that a decrease in tubular sodium chloride concentration (and osmolality) increases the release of renin.
D000263:Adenylate Kinase / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000502:physiology; D066298:In Vitro Techniques; D007678:Kidney Glomerulus / Q000201:enzymology*; D007684:Kidney Tubules / Q000502:physiology*; D007686:Kidney Tubules, Distal / Q000502:physiology*; D008297:Male; D009994:Osmolar Concentration; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012083:Renin / Q000378:metabolism*
D000263:Adenylate Kinase; D012083:Renin; D011188:Potassium; D002118:Calcium