Properties of beta-adrenergic receptors on porcine corpora lutea and granulosa cells.
The nature of beta-adrenergic binding by swine corpora lutea and granulosa cells was examined with the specific beta-adrenergic radioligand, (+/-)3-[125I]iodocyanopindolol (ICYP). Saturation analyses revealed the presence of high affinity (Kd = 15.2 +/- 2.1 pM; n = 8 experiments) and low capacity (6.7 +/- 0.8 fmol/mg protein) beta-adrenergic receptors on porcine corpora lutea membranes. The properties of beta-adrenergic binding were determined by computer modeling of competition studies with a variety of compounds selective for beta-adrenergic subtypes. These studies disclosed predominantly beta 1-adrenergic receptors on pig luteal membranes. This inference from radioligand binding studies was corroborated functionally by the approximately equipotent biological effects of L-norepinephrine and L-epinephrine on cAMP production by luteal tissue (respective EC50s of 282 +/- 31 and 187 +/- 66 nM; n = 3 experiments). Physiological regulation of specific beta-adrenergic receptor content in the swine ovary was indicated by prominent (up to 9-fold) variations in receptor concentrations among corpora lutea and granulosa cells at various stages of maturity. In addition, there was differential expression of beta-adrenergic receptor subtype. Whereas the beta-adrenergic receptor subtype was predominantly beta 1 in corpora hemorrhagica and corpora lutea, granulosa cells and corpora albicantia contained principally beta 2 receptors. This difference could not be accounted for by blood cell contamination of corpora lutea, since swine blood cells contained predominantly (greater than 98%) beta 2-receptors, which were present at less than 8.6% the concentration of total beta-receptors in luteal tissue. In summary, swine corpora lutea and granulosa cells contain specific high affinity, low capacity beta-adrenergic receptors that are functionally coupled to biological responses. Moreover, total receptor content as well as beta-adrenergic subtype exhibit significant physiological variation in relation to maturational status of ovarian follicular and luteal tissue.[1]References
- Properties of beta-adrenergic receptors on porcine corpora lutea and granulosa cells. Perkins, S.N., Cronin, M.J., Veldhuis, J.D. Endocrinology (1986) [Pubmed]
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