ISSN:
0263-6484
Schlagwort(e):
(Na-K)ATPase
;
quantitative cytochemistry
;
dietary sodium
;
adrenalectomy
;
Chemistry
;
Biochemistry and Biotechnology
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Biologie
,
Medizin
Notizen:
A cytochemical method was used to measure total, ouabain insensitive and specific (Na-K)ATPase activities along the rat nephron. Enzyme activity was expressed as per cent of mean integrated extinction with reference to a calibrated filter. The lowest mean values of total, ouabain-insensitive, and (Na-K)ATPase activities were found in the proximal convoluted tubule (PCT). In the distal convoluted tubule (DCT), total and ouabain-insensitive activities (77·8 per cent and 45·8 per cent, respectively) were significantly higher than in the medullary thick ascending limb (MAL) (66·0 per cent and 24·6 per cent, respectively). Mean values of (Na-K)ATPase activity were significantly lower in DCT than in MAL (32·0 per cent and 41·3 per cent, respectively). Using Lineweaver-Burk plots, the KM ATP value for total ATPase activity was found to be 2·33, 1·79, and 3·63 mM in DCT, MAL, and PCT respectively. Maximal velocity was lower in PCT than in MAL and DCT. For (Na-K)ATPase, the smallest KM value was found in MAL (0·95 mM) and was 2·73 and 5·71 mM in DCT and PCT respectively. Maximal velocity was the highest in MAL (49·3 per cent), lower in DCT (36·1 per cent) and least in PCT (22·5 per cent). ATPase was measured in the MAL and DCT from rats fed a normal (N-Na+) or a high (Hi-Na+) sodium diet, and from Hi-Na+ rats one week after adrenalectomy (ADX). In the MAL, (Na-K)ATPase tended to be higher in Hi-Na+ than in N-Na+ rats, but was significantly lower in ADX than in Hi-Na+. A significant correlation was found between daily urinary Na excretion and (Na-K)ATPase in N-Na+ and Hi-Na+ animals (UNa = 0·19 (Na-K)ATPase - 3·10, n = 15, r = 0·53, P 〉 0·05). In the DCT, variations between N-Na+ and ADX rats were minimal. ADX abolished the difference in (Na-K)ATPase between MAL and DCT.In summary, quantitative microdensitometry appears a suitable method for measuring (Na-K)ATPase along the nephron, and this study indicates that the Na content of the diet and adrenal hormones modulate (Na-K)ATPase in the MAL.
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/cbf.290030208
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