Characterization of (/sup 3/H)forskolin binding sites in the iris-ciliary body of the albino rabbit

Journal Article · Fri Jan 01 00:00:00 EST 1988 · Life Sci.; (United States)

DOI:https://doi.org/10.1016/0024-3205(88)90224-X· OSTI ID:5244219

Goldman, M E; Mallorga, P; Pettibone, D J; Sugrue, M F

(/sup 3/H)forskolin binding sites were identified using membranes prepared from the iris-ciliary body of adult, albino rabbits. Scatchard analysis of saturation binding experiments demonstrated that (/sup 3/H)forskolin bound to a single population of high affinity sites. The K/sub d/ and B/sub max/ values were 8.7 +- 0.9 nM and 119.0 +- 30.9 fmolmg prot. using membranes prepared from frozen tissue and 17.0 +- 6.2 nM and 184.4 +- 47.2 fmolmg prot. using fresh tissue. The binding of (/sup 3/H)forskolin was magnesium-dependent. The B/sub max/ was enhanced by sodium fluoride and Gpp(NH)p, a nonhydrolyzable guanine nucleotide analog. Forskolin was the most potent inhibitor of (/sup 3/H)forskolin binding; two commercially-available analogs were weaker inhibitors. In an adenylate cyclase assay, there was the same rank order of potency to enhance enzyme activity. Based upon binding affinities, magnesium-dependence, sensitivity to sodium fluoride and Gpp(NH)p, rank order of potencies of analogs and correlation of binding with adenylate cyclase activity, these studies suggest that the (/sup 3/H)forskolin binding site in the iris-ciliary body is similar to the binding site in other tissues

• Research Organization: Merck Sharp and Dohme Research Laboratories, West Point, PA (USA)
• OSTI ID: 5244219
• Journal Information: Life Sci.; (United States), Vol. 42:13
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
CYCLASES
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PROTEINS
BIOCHEMICAL REACTION KINETICS
RECEPTORS
CELL MEMBRANES
EYES
RABBITS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMALS
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BODY AREAS
CELL CONSTITUENTS
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ORGANS
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550201* - Biochemistry- Tracer Techniques