Human Melanocytes as a Target Tissue for Hormones: In Vitro Studies with 1α-25, dihydroxyvitamin D3, α-melanocyte Stimulating Hormone, and Beta-estradiol

Clinical evidence exists which suggests that normal pigment cell (melanocyte) function is subject to hormonal influences, but the nature of these interactions at a cellular level is poorly understood. We have investigated the effects of the vitamin D-derived secosteroid hormone 1α-25,dihydroxyvitamin D3 (1,25(OH)2D3), the pituitary-derived peptide alpha-melanocyte stimulating hormone (α-MSH), and the sex steroid beta-estradiol on melanocytes cultured from normal human foreskin.Human melanocytes specifically internalized 1,25(OH)2 D3 with high affinity (Kd 0.5 – 0.8nM). Incubation with 1,25(OH)2D3 (10-9M) for 48 h resulted in a 100% increase in 25-hydroxyvitamin D3-24-hydroxylase activity and a 50% increase in tyrosinase activity. There was no significant effect of 1,25(OH)2D3 on intracellular cyclic adenosine monophosphate (cAMP). In contrast to 1,25(OH)2D3, α-MSH at a concentration of 5 × 10-7 M caused a sevenfold increase in intracellular cAMP after 12 min but only a modest increase (