Characteristics of alpha 1-adrenergic receptors in a rat salivary cell line, RSMT-A5.
1. Membrane preparations obtained from RSMT-A5, an established rat submandibular cell line, possess alpha 1-adrenergic receptors as judged by [3H]prazosin binding studies. Scatchard analysis reveals a single class of binding sites with an equilibrium dissociation constant (Kd) of 0.052 nM and a receptor density (Bmax) of 104 fmol/mg protein. 2. These receptors are functional since stimulation by epinephrine results in an increased rate of phosphatidylinositol turnover which is blocked by both phentolamine and phenoxybenzamine. 3. Phenoxybenzamine (10(-5) M) irreversibly blocks 95% of the receptors within 2 min. A kinetic analysis shows that the receptors subsequently reappear at a rate of 6 fmol/mg protein/h. The calculated rate constant for receptor clearance (Kc) is 0.027 hr-1, and the half life (t 1/2) of the receptor is 26 hr. 4. These results are comparable to those reported for alpha 1-adrenergic receptors in the BC3H-1 smooth muscle cell line and suggest that alpha 1-adrenergic receptors in cultured cells, from diverse tissues, display similar characteristics.
He
X J
XJ
Clinical Investigations and Patient Care Branch, National Institute of Dental Research, Bethesda, MD 20892.
Wu
X Z
XZ
Brown
A M
AM
Wellner
R B
RB
Baum
B J
BJ
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D007294:Inositol / Q000378:metabolism; D010643:Phenoxybenzamine / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism / Q000493:pharmacokinetics; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D012469:Salivary Glands / Q000378:metabolism*
D010716:Phosphatidylinositols; D011506:Proteins; D011942:Receptors, Adrenergic, alpha; D010643:Phenoxybenzamine; D007294:Inositol; D011224:Prazosin