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Melatonin receptors in lizard brain were identified and characterized using 125I-labeled melatonin ([125I]MEL) after solubilization with the detergent digitonin. Saturation studies of solubilized material revealed a high affinity binding site, with an apparent equilibrium dissociation constant of 181 +/- 45 pM. Binding was reversible and inhibited by melatonin and closely related analogs, but not by serotonin or norepinephrine. Treatment of solubilized material with the non-hydrolyzable GTP analog, guanosine 5'-(3-O-thiotriphosphate) (GTP-gamma-S), significantly reduced receptor affinity. Gel filtration chromatography of solubilized melatonin receptors revealed a high affinity, large (Mr 400,000) peak of specific binding. Pretreatment with GTP-gamma-S before solubilization resulted in elution of a lower affinity, smaller (Mr 150,000) peak of specific binding. To purify solubilized receptors, a novel affinity chromatography resin was developed by coupling 6-hydroxymelatonin with Epoxy-activated Sepharose 6B. Using this resin, melatonin receptors were purified approximately 10,000-fold. Purified material retained the pharmacologic specificity of melatonin receptors. These results show that melatonin receptors that bind ligand after detergent treatment can be solubilized and substantially purified by affinity chromatography.

As the applications of laparoscopy for general surgical procedures expanded in the 1990s, pregnancy was initially considered a contraindication. Several case reports have suggested the safety of laparoscopy in pregnancy. Previous clinical studies indicate a higher fetal mortality may exist and advised caution. To evaluate the fetal outcome of laparoscopic procedures in pregnant patients at our institution, we retrospectively reviewed the medical records between 1991 and 1997 and identified 21 pregnant patients who underwent either a laparoscopic (n = 12) or open (n = 9) procedure. Appendectomies, cholecystectomies, and diagnostic laparoscopics were performed. Specific variables including age, length of procedure, hospital stay, duration of parenteral analgesic use, gestational age at the time of surgery and delivery, O2 saturation and EtCO2 during surgery, APGAR scores, and birth weights were compared between the two groups. Laparoscopic procedures during pregnancy resulted in shorter hospital stays (34 hours versus 91 hours; P = 0.01), less use of parenteral narcotic analgesics (5 hours versus 29 hours; P = 0.05), and no prolongation of operative times (51 minutes versus 63 minutes; P = 0.20). In addition, laparoscopy was performed at earlier gestational ages (12 weeks versus 29 weeks; P = 0.001). There was one miscarriage 7 days after a laparoscopic cholecystectomy early in the 1st trimester that was not statistically significant. Our experience did not show a higher incidence of fetal loss when comparing laparoscopic to open procedures in pregnant patients.

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