Effects of calcium channel modulators on the regulation of cytoplasmic Ca2+ and hormone secretion of parathyroid cells.
Effects of Ca(2+)-channel modulators were examined in human, bovine and murine parathyroid tissue. In 0.5 mM external Ca2+, 100 microM verapamil inhibited parathyroid hormone release, stimulated uptake and efflux of 45Ca and raised cytoplasmic Ca2+ concentration ([Ca2+]i). However, in 3.0 mM Ca2+ the drug only affected efflux. Methoxyverapamil (50 microM) inhibited parathyroid hormone release in 0.5 mM but stimulated secretion in 3.0 mM Ca2+. BAY K 8644 (10 microM) had similar actions as verapamil on parathyroid hormone release and [Ca2+]i, whereas nifedipine (1 microM) and diltiazem (50-100 microM) lacked effects. Despite the lack of voltage-dependent Ca2+ channels in parathyroid cells, drugs with established actions on such channels affect [Ca2+]i and parathyroid hormone release. However, these actions are not sufficiently pronounced and tissue specific to allow their use for correcting hyperparathyroidism.
Ridefelt
P
P
Department of Surgery, University Hospital, Uppsala, Sweden.
Hellman
P
P
Rastad
J
J
Larsson
R
R
Akerström
G
G
Gylfe
E
E
D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002417:Cattle; D002478:Cells, Cultured; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D005711:Gallopamil / Q000494:pharmacology; D006801:Humans; D008297:Male; D010280:Parathyroid Glands / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley
D002121:Calcium Channel Blockers; D010281:Parathyroid Hormone; D005711:Gallopamil; D002118:Calcium