Protein secretion in lacrimal gland: alpha 1-beta-adrenergic synergism.
We have shown the existence of a homogeneous population of specific binding sites for [3H]prazosin in membranes from rat lacrimal glands. The value of the equilibrium dissociation constant was 0.186 +/- 0.07 nM, and the density of specific binding sites was 20.4 +/- 1 fmol/mg protein. Taking into account the potency sequences for adrenergic agonists and antagonists for competition with these [3H]prazosin binding sites, we identified them as alpha 1-adrenergic receptors. Moreover, we have demonstrated that the stimulation of protein discharge evoked by epinephrine could be partly attributed to the occupation of this alpha-adrenergic receptor subtype. However, the inhibition pattern of the epinephrine effect by a beta-adrenergic antagonist, 1-propranolol, and the characteristics of the secretory response observed when selectively stimulating the alpha 1- and beta-adrenergic receptors, either separately or simultaneously, suggest that 1) a simultaneous activation of both receptors is necessary to produce a maximal secretory response to catecholamines; and 2) a synergism may exist between these two routes of stimulation, leading to an amount of protein discharge higher than that expected in the case of additive effects.
Mauduit
P
P
Herman
G
G
Rossignol
B
B
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D003000:Clonidine / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D007765:Lacrimal Apparatus / Q000378:metabolism*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*
D000317:Adrenergic alpha-Antagonists; D007093:Imidazoles; D011506:Proteins; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D011433:Propranolol; D007545:Isoproterenol; D003000:Clonidine; C014282:cirazoline; D009638:Norepinephrine; D011224:Prazosin; D004837:Epinephrine