Endothelin-induced inositol phosphate formation in rat kidney. Studies on receptor subtypes, G-proteins and regulation during ontogenesis.
The aim of this study was to characterize the properties of endothelin (ET)-receptor subtypes mediating inositol phosphate (IP)-formation in rat kidney and their regulation during ontogenesis. In renal cortical slices of adult rats (12-16 weeks old) ET's concentration-dependently increased IP-formation with an order of potency ET-1 >> ET-3. While the non-selective ET-receptor antagonist bosentan (10 microM) completely suppressed ET-induced IP-formation, the ETA-receptor antagonist BQ-123 (10 microM) inhibited it only by 70%, the ETB-receptor antagonist IRL 1038 (1 microM) by 25%; combined application of BQ-123 + IRL 1038 caused complete inhibition of ET-1-induced IP-formation. Pretreatment of isolated renal cells with pertussis toxin (PTX, 500 ng/ml) overnight did not attenuate but significantly increased ET-1-induced IP-formation. Ontogenetic studies in renal sites from neonatal, 1, 2, 3, 6, 12 and 24 weeks old rats revealed that ET-1-induced IP-formation maturation-dependently declined being highest in neonatal rats (increase: 169% over basal) and lowest in 24 weeks old rats (increase: 47% over basal). This decline in ET-induced IP-formation was accompanied by a decrease in renal ET-receptor number and the amount of immunodetectable Gq/11 (assessed by Western-blotting using the QL-antiserum). Moreover, ET-receptor subtypes changed during the maturation process: from neonates to 12 weeks old rats number and functional responsiveness of ETA-receptors declined, while that of ETB-receptors increased. We conclude that in adult rat renal cortex ET-induced IP-formation is mediated by activation of both ETA- and ETB-receptors and does not involve a PTX-sensitive G-protein. ET-induced IP-formation declines during the maturation process; this is associated with a decrease in ET-receptor number and the immunodetectable amount of Gq/11.
Becker
K
K
Institute of Pharmacology and Toxicology, Martin-Luther University of Halle-Wittenberg, Halle (Saale), Germany.
Erdbrügger
W
W
Heinroth-Hoffmann
I
I
Michel
M C
MC
Brodde
O E
OE
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D000077300:Bosentan; D004305:Dose-Response Relationship, Drug; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D019334:Endothelin-3 / Q000378:metabolism / Q000494:pharmacology; D016232:Endothelins / Q000494:pharmacology; D005260:Female; D019204:GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism; D007295:Inositol Phosphates / Q000096:biosynthesis*; D007672:Kidney Cortex / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D037342:Pertussis Toxin; D051381:Rats; D011921:Rats, Inbred WKY; D017466:Receptors, Endothelin / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D019334:Endothelin-3; D016232:Endothelins; D007295:Inositol Phosphates; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D017466:Receptors, Endothelin; D013449:Sulfonamides; D010566:Virulence Factors, Bordetella; C077420:Cys(11)-Cys(15)-endothelin-1 (11-21); D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000077300:Bosentan; C072247:cyclo(Trp-Asp-Pro-Val-Leu)