Effect of alpha-receptor stimulation on Cl transport by rat submandibular acini.
Dispersed salivary acini isolated from the rat submandibular gland by enzymatic digestion were used to study the effects of alpha-receptor stimulation on transmembrane transport of 36Cl. In the absence of secretagogue, the tracer accumulated in the cells in a time-dependent manner until a steady-state content of 6.8 +/- 0.1 nmol/mg protein was attained after 3-5 min of incubation. Epinephrine (1 mumol/L) alone did not modify 36Cl accumulation but in the presence of the beta-receptor blocker propranolol (1 mumol/L) caused a significant (21%) reduction in the isotope content of the cells to 5.2 +/- 0.1 nmol/mg protein. In acini pre-loaded with 36Cl for 12 min, 1 mumol/L epinephrine caused a rapid but transient net efflux of tracer, but the isotope content subsequently increased to pre-stimulation levels. In the presence of propranolol, however, the efflux of 36Cl induced by epinephrine was larger and more sustained and was partially inhibited by the K-channel blocker quinidine (1 mmol/L) and significantly by the absence of Ca2+ in the incubation medium. The alpha-agonist phenylephrine (10 mumol/L) also significantly reduced the steady-state 36Cl content of tracer-pre-loaded cells. By contrast, exposure of the acini to epinephrine in the presence of the alpha-receptor blocker phentolamine, or the beta-agonist isoproterenol, increased the tracer content of the cells, whether the drugs were added at time zero or to tracer-pre-loaded cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Martinez
J R
JR
Department of Child Health, University of Missouri School of Medicine, Columbia 65212.
Reed
P
P
D000818:Animals; D002712:Chlorides / Q000493:pharmacokinetics*; D004837:Epinephrine / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000378:metabolism; D013363:Submandibular Gland / Q000166:cytology / Q000187:drug effects*
D002712:Chlorides; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D011950:Receptors, Cholinergic; D010656:Phenylephrine; D007545:Isoproterenol; D004837:Epinephrine