The effect of developmental growth on the kidney content of phosphoribosyl pyrophosphate PPRibP was studied in rats at ages between the foetal animal and up to 100 days of age. In addition, the effect of short-term diabetes (up to 14 days) on the renal content of PPRibP was studied in immature rats and in adults aged approx. 60 days. The developmental pattern of PPRibP is such that the PPRibP content is lowest in the young rat and increases as the rate of kidney growth slows. In the adult rat, the early kidney hypertrophy of diabetes is accompanied by a fall in PPRibP content and, again, the PPRibP content returns to normal as the rate of kidney hypertrophy diminishes. Induction of diabetes in the immature rat causes a lesser degree of kidney hypertrophy and also a smaller depression of renal PPRibP content. The activity of PPRibP synthetase (EC 2.7.6.1) is not significantly affected by age or diabetes. The changes in PPRibP content are discussed in relation to the generation of ribose 5-phosphate by the pentose phosphate pathway and the utilization of PPRibP for nucleotide synthesis via the 'de novo' and salvage pathways.
1. Ca2+-adenosine 5'-triphosphatase (Ca2+-Mg2+-ATPase) activity was studied simultaneously in calmodulin-deficient erythrocyte ghost membranes and inside-out vesicles (IOVs) from 12-week-old female spontaneously hypertensive rats (SHR) and their matched controls: [Wistar-Kyoto normotensive rats (WKY)], and in detergent extracts of ghost membranes. 2. Both adenosine 5'-triphosphate (ATP)-dependent Ca2+ uptake by IOVs and Ca2+-dependent ATP hydrolysis activity of ghost membranes were reduced significantly in the SHR compared with WKY, when either the calmodulin-independent or calmodulin-stimulated activities were compared. 3. The ratios between Ca2+ uptake and ATP hydrolysis activities in the SHR remained approximately 1.0, showing a proportional reduction in both activities. 4. No difference in affinity for calmodulin was observed between SHR and WKY. 5. No significant difference in Ca2+-dependent ATP hydrolysis activity was observed between SHR and WKY after detergent solubilization of erythrocyte ghost membranes. 6. These results suggest that the number of Ca2+-Mg2+-ATPase units are similar in SHR and WKY and that the reduced activity in the intact SHR membrane is due to altered membrane environment.
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