cAMP- and beta-adrenergic-stimulated chloride-dependent Ca2+ secretion in frog skin.
This study examined the possible existence and nature of Ca2+ transport in frog skin using 45Ca fluxes and short-circuiting technique. Following the addition to full-thickness frog skin (FTFS) of 8-[p-chlorophenylthio]cAMP (8-CPT-cAMP), forskolin, or 1-methyl-3-isobutylxanthine, the secretory Ca2+ flux increased severalfold, inducing net Ca2+ secretion. The absorptive flux was unchanged. Isoproterenol (10(-6)M) reproduced the effects of cAMP on Ca2+ secretion (-3.76 +/- 0.80 nmol X cm-2 X h-1 vs. +0.04 +/- 0.05 in control) while vasopressin and parathyroid hormone did not alter Ca2+ fluxes. Because FTFS contains subepidermal glands capable of Cl- secretion in response to beta-adrenergic stimulation, split-thickness frog skin (STFS) consisting of the gland-free Na-absorbing surface epithelium was used to localize the anatomic site of Ca2+ secretion. In STFS, addition of 8-CPT-cAMP or isoproterenol failed to induce Ca2+ secretion, suggesting that this transport in FTFS is localized in skin glands. Additional studies explored the relationship between Ca2+ and Cl- transport in FTFS. Furosemide prevented the stimulation of both Ca2+ and Cl- secretion. Removal of Cl- from the bathing medium abolished Ca2+ secretion. Thus, FTFS exhibits a beta-adrenergic, cAMP-stimulated net Ca2+ secretion that is Cl- dependent. As this effect is not observed in STFS, the pathway of Ca2+ secretion in frog skin is probably localized in the subepidermal glandular epithelium in association with Cl- secretion. Frog skin glands may represent a useful model for the study of Ca2+ transport in Cl--transporting epithelia.
F N
FN
Ziyadeh
E
E
Kelepouris
M M
MM
Civan
Z S
ZS
Agus
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002712:Chlorides / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology*; D004553:Electric Conductivity; D005260:Female; D005665:Furosemide / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D010281:Parathyroid Hormone / Q000494:pharmacology; D011894:Rana pipiens; D012867:Skin / Q000378:metabolism*; D013268:Stimulation, Chemical; D013566:Sympathomimetics / Q000494:pharmacology*; D013873:Thionucleotides / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology
D002712:Chlorides; D010281:Parathyroid Hormone; D013566:Sympathomimetics; D013873:Thionucleotides; D014667:Vasopressins; D005576:Colforsin; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000584:Amiloride; D005665:Furosemide; D000242:Cyclic AMP; D007545:Isoproterenol; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine