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Five-sixths nephrectomized rats were used in the evaluation of the effects of potassium depletion on bicarbonate reabsorption in the distal tubules left behind. The regulatory mechanism involved is also examined with the use of proton secretion inhibitors. Results reveal that potassium depletion causes a significant elevation of bicarbonate absorption among partially nephrectomized rats through the stimulation of the hydrogen-ATPase activity.

The transport mechanisms that mediate the ability of angiotensin II (ANG II) to increase bicarbonate reabsorption was analyzed in the late distal tubules (DT) of rats that were exposed to five-sixths nephrectomy (Nx). Western and immunocytochemical analysis in Nx rats indicated the presence of enhanced H+-adenosine triphosphatase expression in the renal cortical tissue. Nx rats also exhibited normal plasma bicarbonate concentrations and ANG II-dependent bicarbonate reabsorption was inhibited by losartan.

The production of monoclonal antibodies to isolated cell wall fragments of Gliocladium roseum, a potential biological control fungus of sap-staining fungi, was described. Two monoclonals, designated 6A5 and 3F12, were characterized and their specificity was assessed by ELISA, immunogold silver staining light microscopy, immunogold electron microscopy and immunoblotting. Since the antibodies also detected specific fungi in wood, they will be of value in analyzing wood colonization byG. roseum.

Levine, David Z., Michelle Iacovitti, Brian Luck, Maxwell T. Hincke, Kevin D. Burns, and James N. Fryer. Surviving rat distal tubule bicarbonate reabsorption: effects of chronic [AT.sub.1] blockade. Am. J. Physiol. Renal Physiol. 278: F476-F483, 2000.--To determine the in vivo effects of chronic ANG II type 1 ([AT.sub.1])-receptor blockade by losartan (Los) on enhanced unidirectional bicarbonate reabsorption ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]) of surviving distal tubules, nephrectomized rats drank either water or a solution of Los, 7 days before microperfusion. [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was suppressed by 50% after Los without further reduction by 5 nM concanamycin A (Conc), suggesting that Los suppresses all Conc-sensitive [H.sup.+]-ATPase pumping. Indeed, ultrastructural analysis of A-type intercalated cells revealed a 50% reduction of [H.sup.+]-ATPase immunogold labeling of the apical plasma membrane, whereas Western blotting showed that [H.sup.+]-ATPase protein levels were also reduced by one-half by Los treatment. To identify other transporters sustaining [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], we perfused three inhibitors simultaneously [5-(N,N,-dimethyl) amiloride hydrochloride, Conc, Schering 28080] with or without prior Los treatment: [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was unchanged despite marked reduction of water reabsorption. We conclude enhanced distal tubule [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] of surviving nephrons is largely mediated by [AT.sub.1] receptor-dependent synthesis and insertion of apical [H.sup.+]-ATPase pumps in A-type intercalated cells. kidney failure; receptors; losartan; proton-transporting adenosine 5'-triphosphate synthase; concanamycin A