Fluid produced and secreted by the Fallopian tube provides the environment in which gamete transport and maturation, fertilization and early embryo development occur. This review describes the composition of oviductal fluid in terms of ions and nutrients such as glucose, lactate, pyruvate and amino acids. The function of oestrogen-specific glycoprotein is discussed. The mechanisms of fluid secretion and agents known to influence fluid production and secretion are described. Clinical implications of abnormal oviductal fluid production and secretion in hydrosalpinx and pelvic inflammatory disease are also discussed.

Cervices from day 18 (D18) intact pregnant rats show significantly greater extensibility and ability to accommodate to extension than cervices from D9 pregnant rats. On D22, cervices from intact pregnant rats show even greater extensibility and accommodation to stretch. Cervices from ovariectomized pregnant rats treated with estrogen (E) and progesterone (P; group OPE) show markedly reduced extensibility and ability to accommodate to stretch compared with intact pregnant cervical tissue (group C) on both D18 and D22. Extensibility of group OPE cervices resembles that of cervices from D9 intact pregnant rats. Cervices from ovariectomized pregnant rats treated with E, porcine relaxin (R), and P (group OPER) or porcine R and P (group OPR) exhibit similar extensibility and ability to accommodate to stretch as cervices from intact pregnant rats on both D18 and D22. The importance of R for cervical softening during pregnancy and its interaction with E near term and during parturition are discussed.

Manchester Ml 3 9PT1 Mechanical and electrophysiological studies of guinea-pig isolated trachealis have been made with the objectives of (a) identifying which of the P-adrenoceptor subtypes mediates the opening of plasmalemmal K+-channels, (b) gaining further insight into the properties of the novel, long-acting Padrenoceptor agonist, salmeterol and (c) clarifying the role of K+-channel opening in mediating the relaxant actions of agonists at P-adrenoceptors. 2 Noradrenaline (10 nM-100 JM) caused a concentration-dependent increase in the rate of beating of guinea-pig isolated atria. The selective P1-adrenoceptor blocking drug, CGP 20712A (100nM-10 JM) caused concentration-dependent antagonism of noradrenaline. The selective P2-adrenoceptor blocking drug, ICI 118551, also produced concentration-dependent antagonism of noradrenaline, but only when used in concentrations greater than 300 nM.3 Cromakalim (100nM-l10 M), isoprenaline (1-100nM), procaterol (0.1-30nM), salbutamol (1 nM-i JlM), salmeterol (1-100 nM) and theophylline (1IlM-1 mM) each caused concentrationdependent suppression of the spontaneous tone of guinea-pig isolated trachealis. 4 ICI 118551 (10 nM-1 JAM) antagonized isoprenaline, procaterol and salmeterol in suppressing the spontaneous tone of the isolated trachea. The antagonism was concentration-dependent. In contrast, ICI 118551 (1 JAM) antagonized neither cromakalim nor theophylline. CGP 20712A (up to 1 JAM) failed to antagonize cromakalim, isoprenaline, procaterol, salmeterol or theophylline. In trachea treated with indomethacin (2.8 JM) and carbachol (10 JAM), salmeterol (1 JAM) antagonized the effects of isoprenaline but not aminophylline. 5 Intracellular electrophysiological recording from guinea-pig isolated trachealis showed that the relaxant effects of cromakalim (10 JM), isoprenaline (100 nM), procaterol (10 nM) and salbutamol (10 nM-1 JAM) were accompanied by the suppression of spontaneous electrical slow waves and by cellular hyperpolarization. In contrast, the relaxant effects of salmeterol (10 nM-1 JiM) were not accompanied by significant cellular hyperpolarization. 6 CGP 20712A (1 AM) inhibited the hyperpolarization but not the relaxation induced by isoprenaline (100 nM). In contrast ICI 118551 (100 nM) inhibited both the hyperpolarization and the relaxation induced by isoprenaline (100 nM). Neither CGP 20712A (1 JAM) nor ICI 118551 (100 nM) inhibited the hyperpolarization induced by cromakalim (10 JM). Salmeterol (1I jaM) inhibited the hyperpolarization induced by isoprenaline (100 nM) but not that induced by cromakalim (1O JAM). 7 It is concluded that activation of either l-or P2-adrenoceptors can promote the opening of K+-channels in the trachealis plasmalemma. The poor ability of salmeterol to hyperpolarize trachealis muscle reflects neither its selectivity in activating P2-adrenoceptors as opposed to P1-adrenoceptors nor a non-specific action in stabilizing the cell membrane. Instead, it may reflect low intrinsic efficacy of the drug at P2-adrenoceptors. The opening of plasmalem...

1 The ability of several potassium (K+) channel openers to inhibit spasm of the uterus of the nonpregnant rat and their susceptibility to antagonism by glibenclamide was assessed in vitro and in vivo. 2 In the isolated uterus exposed to oxytocin (0.2 nM), cromakalim, RP 49356 and pinacidil were of similar potency (mean pD2 = 6.4, 6.0 and 6.2 respectively) while minoxidil sulphate was of lower potency (pD2 = 4.7). Glibenclamide antagonized cromakalim and RP 49356 with the interactions consistent with competitive antagonism (mean pA2 of 6.57 and 7.00 respectively). Glibenclamide also antagonized pinacidil (pA2 = 6.22) but the slope of the Schild plot was significantly greater than -1. Neither salbutamol nor minoxidil sulphate was antagonized by glibenclamide (10p1M). (0.01-1lpM) inhibited spasm evoked by all concentrations of KCl (10-80mM). Suppression of spasm evoked by KCI (10-80mM) by cromakalim (100pM) and pinacidil (100pMm) was insensitive to glibenclamide (10pM).4 Cromakalim (0.1mgkg-1) and RP 49356 (0.1mgkg-1), given by i.v. bolus injection, inhibited uterine contractions, produced a fall in blood pressure and a slight tachycardia in the conscious ovariectomized rat. Glibenclamide (20mgkg-'), given by i.v. infusion, antagonized the vascular and uterine smooth muscle relaxant properties of cromakalim and RP 49356. 5 Several K+ channel openers are uterine relaxants. The antagonism of cromakalim, RP 49356 and pinacidil, at low concentrations, by glibenclamide suggests their actions may involve an ATP-sensitive K+ channel. High concentrations of pinacidil (10 and 100puM) and cromakalim (100pM) may exert an additional action in the uterus. The low potency of minoxidil sulphate and its insensitivity to glibenclamide in the isolated uterus suggests that its mechanism of action may differ from that of the other K+ channel openers.

Changes in the collagen and glycosaminoglycan components of cervical connective tissue were studied in nonpregnant, intact pregnant, and ovariectomized hormone-treated pregnant rats. Collagen concentration and solubility and the concentration of the glycosaminoglycans dermatan sulfate (DS), heparan sulfate, and hyaluronic acid (HA) in cervices taken from day 9 (D9) pregnant rats were similar to those in cervices from nonpregnant rats. In cervical tissue from late pregnant intact control rats on D18 and D22, the collagen concentration decreased, collagen solubility increased, and there was no significant change in total glycosaminoglycan concentration. In cervices from ovariectomized pregnant rats treated with progesterone and estrogen, collagen and glycosaminoglycan parameters resembled those of D9 and nonpregnant cervices on both D18 and D22. However, treatment of ovariectomized pregnant rats with progesterone, estrogen, and porcine relaxin (R) restored cervical collagen concentrations to those of intact controls on both D18 and D22. On D18 of pregnancy, cervical collagen solubility was partially increased by R treatment, and by D22, it was similar to that of intact D22 pregnant controls. R treatment also resulted in a significantly increased cervical concentration of HA. It is concluded that the decrease in collagen concentration, increase in collagen solubility, and increase in HA concentration resulting from R action may contribute in part to the increased extensibility of the cervix that occurs during late pregnancy in the rat.

Length of gestation, duration of labor and delivery, and fetal survival were determined in control intact pregnant rats (group C). Pregnant rats were bilaterally ovariectomized on day 9 and given progesterone (P) implants and, in addition, one of the following injection regimens; estrogen (E; group OPE), E and porcine relaxin (R; group OPER), or porcine R (group OPR). Hormone treatments were given in doses designed to produce serum levels of these hormones similar to those observed in intact pregnant rats. The P implants were removed during the evening of day 21 to mimic the decline in serum P levels that normally occurs as a result of luteolysis. Animals in groups OPE and OPR exhibited significantly prolonged gestation, prolonged duration of labor and delivery, and reduced fetal survival compared with controls. Group OPER animals exhibited slightly but not significantly shorter length of gestation, similar duration of labor and delivery, and similar rate of fetal survival compared to control values. Group OPER animals showed normal maternal behavior and were able to suckle their young.

Porcine relaxin (250 guinea-pig units/mg) infused intravenously into anaesthetized rats at 20 micrograms/h reversibly abolished spontaneous intra-uterine pressure cycles yet left the myometrium responsive to oxytocin in doses of 4--8 mu. The inhibition was found to be primarily of the frequency, rather than of the amplitude, of pressure cycles. Relaxin (5 or 10 micrograms) was capable of completely suppressing uterine activity driven by prostaglandin F2 alpha infusion in oestrogen-treated ovariectomized rats. Whereas the beta-adrenergic blocker, propranolol, had no effect on relaxin-induced inhibition, phentolamine, an alpha-blocker, significantly delayed the relaxin effect. It is unlikely, however, that relaxin operates through an alpha-inhibitory receptor. The results show that relaxin acts primarily as a frequency modulator and is capable of antagonizing an exogenous myometrial stimulant.

In control intact rats (group C), the frequency of intrauterine pressure cycles (IUPC) declines steadily during pregnancy from 80-130 cycles/3 h on day 10 (D10) to 20-30 cycles/3 h on D20. The decline in frequency is due to increasingly prolonged periods of myometrial quiescence, which increase from 30-90 min/3 h on D10 to 120-150 min/3 h by D20. During the 24 h preceding labor, the frequency of IUPC remains at less than 15 cycles/h until 3 h prepartum, when there is an abrupt increase to 30 cycles/h. Ovariectomized pregnant animals treated with progesterone (P) and estrogen (E; group OPE) exhibit significantly greater frequency of IUPC and significantly lower incidence of myometrial quiescence than intact pregnant rats from D12 and for the remainder of pregnancy. Ovariectomized pregnant rats that received P, E, and porcine relaxin (R: group OPER) or P and porcine R only (group OPR) exhibited declining frequency of IUPC similar to that observed in group C animals. Group OPER rats exhibited prolonged periods of myometrial quiescence of similar duration to those observed in control intact rats. In group OPR animals, however, the periods of myometrial quiescence were considerably diminished during late pregnancy. Group OPER animals exhibited a pattern of myometrial activity during labor and postpartum similar to that of control animals. The results suggest an important role for R in the control of myometrial activity during the second half of pregnancy and parturition in the rat.