Adrenomedullin increases the short-circuit current in the rat prostate: Receptors, chloride channels, the effects of cAMP and calcium ions and implications on fluid secretion.

In this study, we have investigated the effects of adrenomedullin on chloride and fluid secretion in the rat prostate. The presence of adrenomedullin (ADM) in rat prostate was confirmed using immunostaining, and the molecular species was determined using gel filtration chromatography coupled with an enzyme-linked assay for ADM. The effects of ADM on fluid secretion were studied by short-circuit current technique in a whole mount preparation of the prostate in an Ussing chamber. The results indicated that the ADM level was higher in the ventral than the dorso-lateral prostate and the major molecular species was the active peptide. ADM increased the short-circuit current through both the cAMP- and calcium-activated chloride channels in the ventral lobe, but only through the calcium-activated channels in the dorso-lateral lobe. These stimulatory effects were blocked by the calcitonin gene-related peptide (CGRP) receptor antagonist, hCGRP8-37. We conclude that ADM may regulate prostatic fluid secretion through the chloride channels, which may affect the composition of the seminal plasma bathing the spermatozoa and hence fertility.

Adrenomedullin increased the short-circuit current in the pig oviduct through chloride channels via the CGRP receptor: mediation by cAMP and calcium ions but not by nitric oxide.

The oviduct serves as a site for the fertilization of the ovum and the transport of the conceptus down to the uterus for implantation. In this study, we investigated the presence of adrenomedullin (ADM) and its receptor component proteins in the pig oviduct. The effect of ADM on oviductal secretion, the specific receptor, and the mechanisms involved were also investigated. The presence of ADM and its receptor component proteins in the pig oviduct were confirmed using immunostaining. Short-circuit current (I(sc)) technique was employed to study chloride ion secretion in the oviductal epithelium. ADM increased I(sc) through cAMP- and calcium-activated chloride channels, and this effect could be inhibited by the CGRP receptor antagonist, hCGRP8-37. In contrast, the nitric oxide synthase inhibitor, L-NG-nitroarginine methyl ester (L-NAME), could not block the effect of ADM on I(sc). In summary, ADM may increase oviductal fluid secretion via chloride secretion independent of the nitric oxide pathway for the transport of sperm and the conceptus.

L-cysteine-capped CdTe quantum dots as a fluorescence probe for determination of cardiolipin.

This paper described the investigation of surface-modified quantum dots (QDs) as a fluorescence probe for the detection of cardiolipin. A single-step method for preparation of non-toxic and photo-stable cadmium telluride (CdTe) QDs capped by L-cysteine in aqueous solution was developed. The prepared QDs were characterized by high-resolution transmission electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectrometry and spectrofluorometry. These functional QDs were used as a fluorescence probe for cardiolipin determination based on the fluorescence quenching. The optimum fluorescence intensity was found to be at pH 7.4 with QDs concentration of 4 x 10(-5) mol L(-1). The effect of other phospholipids on the intensity of CdTe QDs showed a low interference response. Under optimized conditions, the quenched fluorescence intensity was linear with the concentration of cardiolipin in the range of 1.33 x 10(-7) - 10.4 x 10(-7) mol L(-1) (r = 0.9976) and a detection limit (S/N = 3) of 18.5 nmol L(-1). The proposed method was applied to the determination of cardiolipin content of HepG2 cell samples before and after oxidative stress with satisfactory results.

Effect of leptin on motility, capacitation and acrosome reaction of human spermatozoa.

Leptin is a polypeptide hormone with important roles in reproduction. It has been detected in human seminal plasma as well as on human ejaculated spermatozoa. This study aimed at studying the possible role of leptin in regulating human sperm functions. Immunofluorescent staining was used to study the expression of leptin and its receptor. The correlation between the concentration of leptin and soluble leptin receptor (ObRs) in seminal plasma as measured by enzyme-linked immunosorbant assay and sperm motility parameters measured by computer-assisted sperm analysis (CASA) was determined. The effects of recombinant leptin on human sperm motility, capacitation and acrosome reaction as measured by chlortetracycline staining were also studied. Leptin immunoreactivity was demonstrated at the equatorial and neck regions of human spermatozoa, whereas that of ObRs was shown up on the tail. After Percoll separation, spermatozoa with high density had more intense leptin immunoreactivity compared with those with low density. No significant correlation was found between seminal plasma concentration of leptin/ObRs and sperm motility parameters. After incubation with recombinant human leptin for either 3 h or overnight, there was no change in all the CASA motility parameters determined and percentages of capacitated and acrosome-reacted spermatozoa. We concluded that leptin does not have a significant effect on motility and capacitation/acrosome reaction in human ejaculated mature spermatozoa. Its role in male reproduction is yet to be determined.

Protection of sperm DNA against oxidative stress in vivo by accessory sex gland secretions in male hamsters.

Reactive oxygen species scavengers present in male accessory sex gland secretions might afford antioxidant protection to sperm DNA. This study was conducted to determine whether accessory sex gland secretions protect the genome and function of spermatozoa against oxidative damage in the uterus. Male golden hamsters were divided into four experimental groups: (i) all accessory sex glands removed; (ii) ampullary glands removed; (iii) ventral prostate gland removed and (iv) sham-operated controls. Ejaculated spermatozoa recovered from uteri 15-30 min after mating with experimental males and caput and cauda epididymal spermatozoa obtained from intact males were incubated in 0-20 mmol NADPH l(-1) for 2 h. These spermatozoa and untreated uterine spermatozoa were processed for two types of comet assay (single cell gel electrophoresis): alkaline comet assay (pH > 13) which revealed single-strand DNA breakage and neutral comet assay (pH 9) which revealed double-strand DNA breakage. In comparison with the sham-operated controls, spermatozoa that had not been exposed to accessory sex gland secretions had a higher incidence and more extensive single-strand DNA damage with increasing concentrations of NADPH. Spermatozoa from hamsters without ampullary glands and from hamsters without the ventral prostate glands were similar to those of the control group. After incubation with NADPH, the capacity of spermatozoa from hamsters without accessory glands and from sham-operated controls to fuse with oocytes in vitro was reduced. However, only hamsters without accessory glands showed a negative correlation between single-strand DNA damage and sperm-oocyte fusion. Cauda epididymal spermatozoa were less susceptible to NADPH treatment compared with caput epididymal spermatozoa. The results of the present study showed that male accessory sex gland secretions can preserve the integrity of the sperm genome.