Open AccessThe binding sites of the calcium antagonist [ 3 H] PN 200110 in the human myometrium and myosalpinx
Author(s) -
Kleinstein Jürgen,
Betjemann Peter,
Weidacher Anne
Publication year - 1986
Publication title -
acta obstetricia et gynecologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.401
H-Index - 102
eISSN - 1600-0412
pISSN - 0001-6349
DOI - 10.3109/00016348609157029
Subject(s) - nitrendipine , myometrium , calcium , endocrinology , medicine , antagonist , binding site , nifedipine , dihydropyridine , receptor , chemistry , uterus , biochemistry
Calcium antagonists of the dihydropyridine type may prove to be an important adjunct to the therapy of premature labor due to their proven ability to inhibit uterine contractility. Specific binding sites for calcium blockers were concentrated in 45 000 × g membrane preparations of human myometrium and myosalpinx. Scatchard plot analysis of the binding of [ 3 H] PN 200110, a benzoxadiazole‐substituted dihydropyridine derivate, revealed that the binding sites of myometrial membranes numbered between 500 and 700 fmoles/mg protein (B max ) and had an affinity (K D ) of 0.3±0.1 nmol/1. In myosalpingeal membrane preparations B max was between 250 and 300 fmoles/mg protein, with KD values of 0.9±0.1 nmol/1. Unlabelled calcium anta‐gonits displaced [ 3 H] PN 200110 binding in the following order of potency ranking: nitrendipine±nifedipine±d‐cisdiltiazem >D‐600±tiapamil. The calcium channels were especially dense (796±186 fmoles/mg protein) in the myometrium of the dorsal uterine wall. The number of binding sites in the myosalpinx was greatest in the isthmus (242±23 fmoles/mg protein).