ABSTRACT
The possibility that phospholipid deacylation may be a critical event in the 12-O-tetradecanoylphorbol-13-acetate (TPA)-associated effects on mouse skin prompted us to examine in vitro the effects of TPA on arachidonic acid metabolism in neonatal mouse keratinocytes. Three-day old neonatal keratinocytes were prelabeled with [14C]arachidonic acid ([14C]AA) and [14C] stearic acid ([14C]ST) and used to characterize the lipases that were activated when these cells were treated with TPA in culture. Data from these studies demonstrate that phosphatidylcholine (PC) and phosphatidylinositol (PI) are the major phospholipids that undergo early hydrolysis to release arachidonic acid when challenged by TPA. Of particular interest was the novel observation of the hydrolysis of 14C-labeled PI in these keratinocytes, the accumulation of [14C]1,2-diacylglyceride and the lack of the [14C]diacylglyceride phosphorylation to form [14C]phosphatidic acid. This lack of [14C] phosphatidic accumulation implied that although TPA enhanced the hydrolysis of [14C]PI resulting in increased [14C]diacylglyceride it did not enhance the resynthesis of the [14C]PI via the phosphorylation of the [14C]diacylglyceride. Therefore, TPA probably is not involved in the turnover of PI in these cells but is involved in the activation of PC hydrolyzing phospholipase A2 and PI hydrolyzing phospholipase C in these keratinocytes releasing arachidonic acid which then undergoes oxygenation reactions to provide biologically active eicosanoids.
Subject(s)
Phorbols/pharmacology , Phospholipids/metabolism , Skin/cytology , Tetradecanoylphorbol Acetate/pharmacology , Animals , Arachidonic Acid , Arachidonic Acids/metabolism , Carbon Radioisotopes , Cells, Cultured , Eicosanoic Acids/metabolism , Lipoxygenase/metabolism , Membrane Lipids/metabolism , Mice , Mice, Inbred BALB C , Skin/metabolism , Stearic Acids/metabolismABSTRACT
Hyperpigmentation in lesions of tinea versicolor has previously been reported to be a result of the effects of the fungus Pityrosporon orbiculare on melanosome formation and distribution. Examination of biopsy specimens from lesions of hyperpigmented tinea versicolor involving vitiliginous skin reveals an absence of melanosomes and melanocytes. Reddish-tan and fawn-colored hyperpigmentation in tinea versicolor of this type is not due to melanin pigment. The possible nature of the pigmentation that delineates hyperpigmented tinea versicolor from normal skin is discussed.
Subject(s)
Tinea Versicolor/pathology , Vitiligo/pathology , Aged , Humans , Male , Microscopy , Microscopy, Electron , Skin Pigmentation , Tinea Versicolor/complications , Vitiligo/complicationsABSTRACT
The induction of follicular growth, ovulation, and atresia by heterologous gonadotropic preparations was studied late in the reproductive cycle of the adult female guinea pig. Human chorionic gonadotropin (HCG) administration (10 IU) 12 days following the first signs of opening of the vaginal membrane was found to stimulate ovulation within 24 h in all animals studied, as evidenced by recovery of ova from their oviducts as well as the presence of postovulatory follicles in their ovaries. Histologically, ovaries of animals receiving HCG exhibited atretic changes in most of the follicles smaller than 999 micrometer in diameter. Pregnant mares serum gonadotropin (PMSG, 10 IU) administered on days 9 and 10 of the cycle was not sufficient to stimulate ovulation in this species although histological changes in the follicular complement were observed. Administration of PMSG prior to the HCG appeared to have an inhibitory effect on ovulation induction. Follicles luteinizing with entrapped ova were seen in all groups receiving exogenous gonadotropin, although they were most prevalent in the animals receiving the maximum total gonadotropin doses (i.e. PMSG + HCG).
