The ontogeny of [3H]nitrendipine binding sites and 45Ca2+ uptake processes in brain synaptosomes from spontaneously hypertensive rats.

Potassium-stimulated 45Ca2+ uptake into rat brain cerebral cortex synaptosomes was measured in spontaneously hypertensive rats at ages two days to 140 days. The fast and slow phases of 45Ca2+ uptake were measured. The slow phase was abolished by replacement of Na+ by choline, was more sensitive to 3,4-dichlorobenzamil and likely represents Na+:Ca2+ exchange. The fast and slow phases of 45Ca2+ uptake developed at different rates, the slow phase developing more rapidly and being more prominent at younger ages, but both phases were at a maximum at 5 weeks. [3H]Nitrendipine binding increased from 2 days (Bmax = 39 +/- 1 fmol mg-1 protein), without change in Kd (mean = 130 +/- 7 X 10(-12) M). Development of [3H]nitrendipine binding paralleled that of the fast phase of 45Ca2+ uptake. Neither 45Ca2+ uptake (both phases) nor [3H]nitrendipine binding (Bmax) changed between 5 weeks (prehypertensive) and 20 weeks (established hypertensive) of age.