title: Effects of gadolinium and cadmium on the electrically evoked release of 45calcium from the isolated rat neurohypophysis.
abstract: Isolated neural lobes of the rat pituitary gland were fixed by their stalks to a platinum wire electrode. They were loaded with 45calcium and then superfused with radioactivity-free Krebs-solution. The efflux of 45calcium into the superfusion medium was determined. After 54-60 min of superfusion the spontaneous outflow of 45calcium was 2.03%/min of the tissue 45calcium. It was not affected by cadmium (Cd2+, 0.03-3 mmol/l), but reduced by 40% in the presence of 1 mmol/l gadolinium (Gd3+). Electrical stimulation with pulses of 15 Hz (3 times for 1 min with intervals of 1 min) evoked a 45calcium release of 14.4% of the tissue radioactivity. The evoked release of 45calcium was reduced by 80% in the presence of tetrodotoxin and by about 50% in the presence of gallopamil (D600, 30 mumol/l) or after omission of unlabelled calcium from the superfusion medium. Gd3+ concentration-dependently reduced the evoked release by maximally 75% at 3 mmol/l. However, it inhibited the evoked release of 45calcium less effectively than the release of vasopressin evoked by identical stimulation conditions. Cd2+ reduced the evoked release by maximally 55% at 300 mumol/l. The effect of Cd2+ on the evoked release of vasopressin was not tested because Cd2+ markedly increased the spontaneous outflow of vasopressin. When the stimulation was carried out for only 1 min at 15 Hz (i.e. 900 pulses) the evoked release of 45calcium was 10.6% of the tissue 45calcium and 100 mumol/l Cd2+ or 300 mumol/l Gd3+ caused a reduction of the evoked release similar to that observed when 3 periods of stimulation were applied.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology, University of Mainz, Federal Republic of Germany.
authors.forename: K
authors.initials: K
authors.lastname: Racké
authors.forename: B
authors.initials: B
authors.lastname: Hering
authors.forename: U
authors.initials: U
authors.lastname: Hochgesand
mesh_terms: D000818:Animals; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D004558:Electric Stimulation; D005260:Female; D005682:Gadolinium / Q000494:pharmacology*; D066298:In Vitro Techniques; D010121:Oxytocin / Q000378:metabolism; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D014667:Vasopressins / Q000378:metabolism
chemical_list: D002132:Calcium Radioisotopes; D002104:Cadmium; D014667:Vasopressins; D010121:Oxytocin; D005682:Gadolinium; D002118:Calcium