Mario Carranza

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1. The aim of this study was to investigate the mechanism of control of Na+,K+-ATPase activity by the cAMP-protein kinase A (PKA) pathway in rat proximal convoluted tubules. For this purpose, we studied the in vitro action of exogenous cAMP (10-3 M dibutyryl-cAMP (db-cAMP) or 8-bromo-cAMP) and endogenous cAMP (direct activation of adenylyl cyclases by 10-5(More)
Phosphorylation of the alpha-subunit of Na+,K(+)-ATPase plays an important role in the regulation of this pump. Recent studies suggest that insulin, known to increase solute and fluid reabsorption in mammalian proximal convoluted tubule (PCT), is stimulating Na+,K(+)-ATPase activity through the tyrosine phosphorylation process. This study was therefore(More)
In rat proximal convoluted tubule (PCT), activation of protein kinase C (PKC) by phorbol 12,13-dibutyrate (PDBu) was previously reported to inhibit Na(+)-K(+)-ATPase, a paradoxical finding in view of the known stimulatory effect of PKC on Na+ reabsorption. Because this inhibition occurs via phospholipase A2 activation, a pathway stimulated by hypoxia, we(More)
We have previously shown that, in oxygenated rat kidney proximal convoluted tubules (PCT), activation of protein kinase C (PKC) by phorbol 12,13-dibutyrate (PDBu) directly stimulates Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity. PKC modulation of Na(+)-K(+)-ATPase activity by phosphorylation of its alpha-subunit was the postulated mechanism. The(More)
Insulin has been shown to stimulate the rate of ouabain-sensitive 86Rb influx in the isolated rat proximal convoluted tubule (PCT). To study the mechanism of this activation of Na-K-adenosinetriphosphatase (Na-K-ATPase), we determined the actions of insulin on 1) the maximal activity (Vmax) of Na-K-ATPase hydrolytic activity; 2) the maximal rate of(More)
BACKGROUND In rat kidney medullary thick ascending limb of Henle's loop (MTAL), activation of protein kinase A (PKA) was previously reported to inhibit Na+,K(+)-ATPase activity. This is paradoxical with the known stimulatory effect of cAMP on sodium reabsorption. Because this inhibition was mediated by phospholipase A2 (PLA2) activation, a pathway(More)
1. In the rat kidney proximal convoluted tubule, epidermal growth factor and insulin have been reported to stimulate Na+ reabsorption. Because most of the effects of these growth factors are mediated by a process of tyrosine phosphorylation and Na+,K(+)-ATPase drives Na+ reabsorption, the influence of tyrosine kinases and tyrosine phosphatases on(More)
We investigated in intact cortical kidney tubules the role of PKA-mediated phosphorylation in the short-term control of Na+,K+-ATPase activity. The phosphorylation level of Na+,K+-ATPase was evaluated after immunoprecipitation of the enzyme from 32P-labelled cortical tubules and the cation transport activity of Na+,K+-ATPase was measured by(More)
The alpha1 subunit of Na,K-ATPase is phosphorylated at Ser-16 by phorbol ester-sensitive protein kinase(s) C (PKC). The role of Ser-16 phosphorylation was analyzed in COS-7 cells stably expressing wild-type or mutant (T15A/S16A and S16D-E) ouabain-resistant Bufo alpha1 subunits. In cells incubated at 37 degrees C, phorbol 12, 13-dibutyrate (PDBu) inhibited(More)
Previous studies have demonstrated the presence of two populations of Na,K-ATPase with distinct kinetic, pharmacological and immunological characteristics along the rabbit nephron, indicating that the proximal segments of the nephron express exclusively the α 1 isoform of the catalytic subunit, whereas the collecting duct expresses an α 3-like isoform.(More)