Ins(1,4,5)P3 induces Ca2+ release from brain microsomes loaded either by the Ca2+ ATPase or by the Na+/Ca2+ exchanger.
In this study we investigated the release of Ca2+ in brain microsomes after Ca2+ loading by the Ca(2+)-ATPase or by the Na+/Ca2+ exchanger. The results show that in microsomes loaded with Ca2+ by the Ca(2+)-ATPase, Ins(1,4,5)P3 (5 microM) released 21 +/- 2% of the total Ca2+ accumulated, and that in the microsomes loaded with Ca2+ by the Na+/Ca2+ exchanger, Ins(1,4,5)P3 released 28 +/- 3% of the total Ca2+ accumulated. These results suggest that receptors of Ins(1,4,5)P3 may be co-localized with the Na+/Ca2+ exchanger in the endoplasmic reticulum membrane or that there are Ins(1,4,5)P3 receptors in the plasma membrane where the Na+/Ca2+ exchanger is normally present, or both. We also found that Ins(1,4,5)P3 inhibited the Ca(2+)-ATPase by 33.7%, but that it had no significant effect on the Na+/Ca2+ exchanger.
Cristóvão
A J
AJ
Centro de Neurociências de Coimbra, Universidade de Coimbra, Portugal.
Carvalho
C A
CA
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D015544:Inositol 1,4,5-Trisphosphate; D012964:Sodium; D000252:Calcium-Transporting ATPases; D002118:Calcium