PI-PLCbeta is involved in the modulation of the proximal tubule Na+-ATPase by angiotensin II.

In previous papers we showed that Ang II increases the proximal tubule Na+-ATPase activity through AT1/PKC pathway [L.B. Rangel, C. Caruso-Neves, L.S. Lara, A.G. Lopes, Angiotensin II stimulates renal proximal tubule Na+-ATPase activity through the activation of protein kinase C. Biochim. Biophys. Acta 1564 (2002) 310-316, L.B.A. Rangel, A.G. Lopes, L.S. Lara, C. Caruso-Neves, Angiotensin II stimulates renal proximal tubule Na+)-ATPase activity through the activation of protein kinase C. Biochim. Biophys. Acta 1564 (2002) 310-316]. In the present paper, we study the involvement of PI-PLCbeta on the stimulatory effect of angiotensin II (Ang II) on the proximal tubule Na+-ATPase activity. Western blotting assays, using a polyclonal antibody for PI-PLCbeta, show a single band of about 150 KDa, which correspond to PI-PLCbeta isoforms. Ang II induces a rapid decrease in PIP2 levels, a PI-PLCbeta substrate, being the maximal effect observed after 30 s incubation. This effect of Ang II is completely abolished by 5 x 10(-8) M U73122, a specific inhibitor of PI-PLCbeta. In this way, the effect of 10(-8) M Ang II on the proximal tubule basolateral membrane (BLM) Na+-ATPase activity is completely abolished by 5 x 10(-8) M U73122. The increase in diacylglycerol (DAG) concentration, an product of PI-PLCbeta, from 0.1 to 10 nM raises the Na+-ATPase activity from 6.1+/-0.2 to 13.1+/-1.8 nmol Pi mg(-1) min(-1). This effect is similar and non-additive to that observed with Ang II. Furthermore, the stimulatory effect of 10 nM DAG is completely reversed by 10(-8) M calphostin C (Calph C), an inhibitor of PKC. Taken together these data indicate that Ang II stimulates the Na+-ATPase activity of proximal tubule BLM through a PI-PLCbeta/PKC pathway.

Angiotensin II stimulates renal proximal tubule Na(+)-ATPase activity through the activation of protein kinase C.

Recently, our group described an AT(1)-mediated direct stimulatory effect of angiotensin II (Ang II) on the Na(+)-ATPase activity of proximal tubules basolateral membranes (BLM) [Am. J. Physiol. 248 (1985) F621]. Data in the present report suggest the participation of a protein kinase C (PKC) in the molecular mechanism of Ang II-mediated stimulation of the Na(+)-ATPase activity due to the following observations: (i) the stimulation of protein phosphorylation in BLM, induced by Ang II, is mimicked by the PKC activator TPA, and is completely reversed by the specific PKC inhibitor, calphostin C; (ii) the Na(+)-ATPase activity is stimulated by Ang II and TPA in the same magnitude, being these effects abolished by the use of the PKC inhibitors, calphostin C and sphingosine; (iii) the Na(+)-ATPase activity is activated by catalytic subunit of PKC (PKC-M), in a similar and nonadditive manner to Ang II; and (iv) Ang II stimulates the phosphorylation of MARCKS, a specific substrate for PKC.

Regulation of the renal proximal tubule second sodium pump by angiotensins

For several years it was believed that angiotensin II (Ang II) alone mediated the effects of the renin-angiotensin system. However, it has been observed that other peptides of this system, such as angiotensin-(1-7) (Ang-(1-7)), present biological activity. The effect of Ang II and Ang-(1-7) on renal sodium excretion has been associated, at least in part, with modulation of proximal tubule sodium reabsorption. In the present review, we discuss the evidence for the involvement of Na+-ATPase, called the second sodium pump, as a target for the actions of these compounds in the regulation of proximal tubule sodium reabsorption

Isolamento de corynebacterium diphtheriae de úlceras cutâneo-mucosas por Leishmania / Isolation of Corynebacterium diphtheriae from mucocutaneous ulcers due to Leishmania

Descrevemos o isolamento do C. diphtheriae em uma regiäo endêmica da leishmaniose cutâneo-mucosa por Leishmania braziliensis braziliensis. Materiais das lesöes cutâneas foram obtidos de dezesseis pacientes. Nove deles foram portadores do bacilo (56%). Os microrganismos suspeitos foram identificados pelos testes de fluorescência sob luz ultravioleta, teste de virulência "in vitro" (por imunodifusäo radial simples), pesquisa da enzima pirazina-carboxilamidase (Pyz) e por imunofluorescência direta e indireta