Regulation of phosphate transport by second messengers in capillaries of the blood-brain barrier.
Regulation of phosphate uptake by the blood-brain barrier was studied in isolated bovine capillaries. Dibutyryl cAMP, in the presence of 3-isobutylmethylxanthine, resulted in a dose-dependent inhibition of phosphate uptake. Phosphate influx, with or without 3-isobutylmethylxanthine, was not different. Inhibition of phosphate uptake was also observed when capillaries were preincubated with isoproterenol, parathyroid hormone, insulin and acidic or basic fibroblast growth factors. Treatment of capillaries with vasoactive intestinal peptide, prostaglandin E1, angiotensin II, epidermal growth factor and phorbol esters did not affect phosphate transport. Endothelin I increased phosphate uptake by 15%. Preincubation with cholera toxin also resulted in a dose-dependent decrease in phosphate uptake. In addition, pertussis toxin inhibited phosphate transport by 29%, but only in the presence of 3-isobutylmethylxanthine. These results demonstrate that generation of second messengers, following receptor stimulation, can induce physiological effects on capillary phosphate influx and suggest that G proteins may modulate this transport.
Dallaire
L
L
Laboratoire de membranologie, Université du Québec à Montréal, Canada.
Giroux
S
S
Béliveau
R
R
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001812:Blood-Brain Barrier; D003994:Bucladesine / Q000494:pharmacology; D002196:Capillaries / Q000378:metabolism*; D002417:Cattle; D002540:Cerebral Cortex / Q000098:blood supply; D002772:Cholera Toxin / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology; D006728:Hormones / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology; D037342:Pertussis Toxin; D010703:Phorbol Esters / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D006133:Growth Substances; D006728:Hormones; D010281:Parathyroid Hormone; D010703:Phorbol Esters; D010710:Phosphates; D010566:Virulence Factors, Bordetella; D003994:Bucladesine; D002772:Cholera Toxin; D037342:Pertussis Toxin; D007545:Isoproterenol; D015056:1-Methyl-3-isobutylxanthine