Effect of dehydration on angiotensin receptors in the AT-1a knockout mouse
Changes in sodium/electrolyte status regulate angiotensin (Ang) receptor expression. Experiments were performed to determine the effect of dehydration on anterior pituitary (AP) and adrenal glomerulosa (AG) and medulla (AM) Ang receptors in AT-1aa knockout [KO(-/-)] and wild type mice [KO(+/+)]. Group Pituitary Adrenal-Glom Adrenal -Med KO(+/+)-W 41 ± 7 274 ± 59 539 ± 70 KO(+/+)-D 86 ± 14* 236 ± 54 617 ± 36 KO(-/-)-W 10 ± 2 51 ± 8 344 ± 86 KO(-/-)-D 9 ± 1 42 ± 7 482 ± 79 W = water ad lib, D = 2 days dehydration, fmol/mg protein Dehydration produced an increase in AP Ang receptors (>90% AT-1 subtype) in wild type mice. There was little specific binding in the KO mice, indicating few if any AT-1a, AT1-b or AT-2 receptors and no effect of dehydration. Dehydration produced no change in adrenal receptors in either group. In wild type mice, AT-2 receptors averaged 20-22% of the receptor pool in the AG and 50-60% in the AM. The proportion of AT-2 receptors was higher in KO mice (50% and 85% in AG and AM, respectively). Residual AT-1 binding in the AG is probably attributed to AT-1b receptors. These results show: 1) a relationship between volume status and pituitary Ang receptors in mice and 2) little evidence for Ang AT-1b receptors in the anterior pituitary or adrenal medulla of AT-1a KO mice.
Morris, M; Li, P; Callahan, MF; Bosch, SM; Coffman, TM; Oliverio, MI; Diz, DI
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