Effect of cocaine on the contractile response to noradrenaline in the epididymal and prostatic regions of the vas deferens

In the prostatic half of the rat vas deferens, the response to noradrenaline under the cocaine effect revealed a phasic and a tonic components, whereas in the epididymal portion of the vas deferens there only occurred the tonic component. Cocaine increased the maximal tonic contractile response to noradrenaline in the epididymal portion and the maximal phasic response--in the prostatic one. Mechanisms of direct postsynaptic action of cocaine are discussed.     

Influence of carbachol on the kinetic parameters of the contractile response to noradrenaline in the rat vas deferens

Graphic and mathematical analysis of kinetics of the rat vas deferens contractile response to noradrenaline showed that alpha1-adrenoceptors mediating the contraction were in different functional states. In some organs, these receptors were homogeneous with the Hill coefficient n = 1 (the linear mode of the Scatchard plot), in the others--not homogeneous, with n > 1 (not linear mode of the Scatchard plot). Carbachol increased the contractile response to noradrenaline. As in the control, two types of response were revealed: 1. The Hill coefficient n < 1 (biphasic mode of the Scatchard plot) with two pools (high and low affinity) of alpha1-adrenoceptors, and 2. The Hill coefficient n = 1 (the linear mode of the Scatchard plot). These results suggest that the influence of carbachol is caused by the local interaction of M-cholinergic and alpha1-adrenergic systems.     

Cellular mechanism underlying the facilitation of contractile response of vas deferens smooth muscle by sodium orthovanadate

Hydrogen sulfide (H(2)S) has been shown to exert cardioprotective effects. However, the roles of extracellular signal-regulated protein kinases 1/2 (ERK1/2) in H(2)S-induced cardioprotection have not been completely elucidated. In this study, cobalt chloride (CoCl(2)), a chemical hypoxia mimetic agent, was applied to treat H9c2 cells to establish a chemical hypoxia-induced cardiomyocyte injury model. The results showed that pretreatment with NaHS (a donor of H(2)S) before exposure to CoCl(2) attenuated the decreased cell viability, the increased apoptosis rate, the loss of mitochondrial membrane potential (ΔΨm), and the intracellular accumulation of reactive oxygen species (ROS) in H9c2 cells. Exposure of H9c2 cells to CoCl(2) or hydrogen peroxide (H(2)O(2)) upregulated expression of phosphorylated (p) ERK1/2, which was reduced by pretreatment with NaHS or N-acetyl-L-cysteine, a ROS scavenger. More importantly, U0126, a selective inhibitor of ERK1/2, mimicked the above cytoprotection of H(2)S against CoCl(2)-induced injury in H9c2 cells. In conclusion, these results indicate that H(2)S protects H9c2 cells against chemical hypoxia-induced injury partially by inhibiting ROS-mediated activation of ERK1/2.     

Carbachol effect on kinetics of the alpha1-adrenergic contractile response of the rat vas deferens

Analysis of the control kinetics of the rat vas deferens contractile response to phenylephrine showed that alpha 1-adrenoceptors mediating the contraction could be in different functional states. In some organs these receptors represented a single pool with Hill coefficient n = 1 (the linear mode of the Scatchard plot), in others--not a single pool, n > 1 (not linear mode of the Scatchard plot). Activation of muscarinic cholinergic receptors by carbachol exerted a stimulating effect on the alpha 1-adrenergic contractile response especially to low adrenomimetic concentrations and the maximum response was increased. The action of cholinomimetic was accompanied by a decrease of Hill coefficient. When the control represented a single pool of alpha 1-adrenoceptors in the presence of carbachol Scatchard plot became biphasic with Hill coefficient n < 1, in addition to the low affinity pool the high affinity appeared. In case of not homogeneous control pool, in the presence of carbachol a single pool was revealed and n was close to 1. These findings suggest that the stimulatory effect of carbachol is caused by its modulator action on the alpha 1-adrenoceptors states and activating influence on the intracellular effector's system.     

A pharmacological investigation of the biphasic nature of the contractile response of rabbit and rat vas deferens to field stimulation

It has been demonstrated previously with the vas deferens of the guinea-pig that the first and second phases of the contractile response to motor nerve stimulation are preferentially antagonized by the P₂-purinoceptor antagonist arylazido aminopropionyl ATP (ANAPP₃), and the α₁-adrenoceptor antagonist prazosin, respectively. We have now investigated the effect of the two antagonists on the biphasic contraction in the vas deferens of two other species; rabbit and rat. ANAPP₃, in a concentration which antagonized responses to exogenously applied ATP but not those to exogenous norepinephrine, preferentially reduced the initial phasic response of the rabbit vas deferens to motor nerve stimulation without significantly reducing the secondary, tonic phase of the response. Prazosin had the opposite effect; antagonizing the response to norepinephrine but not to ATP and reducing the tonic response to motor nerve stimulation without significantly reducing the initial phasic response. Results obtained with the rat vas deferens were similar. The present results combined with previous findings suggest that ATP and norepinephrine act as cotransmitters in the vas deferens of several species.     

Release of contractile agents from rat vas deferens by clonidine.

Clonidine induces contractile effects on the isolated rat vas deferens, but not on rat uterus or guinea-pig ileum. However, we have observed that if clonidine is incubated for about 10 min with a nutrient solution containing an isolated rat vas deferens, the resulting solution can contract an isolated rat uterus, or guinea-pig ileum indicating the involvement of a substance released from the vas. This contractile effect was partially reduced by naloxone and by serotonin antagonists, and by using a denervated vas, indicating that opioids, serotonin and eventually other substances released from nerve tissue of the vas can be involved.     

The androgenic effect of norethisterone and 5alpha-norethisterone on the contractile response of the rat vas deferens to methoxamine and serotonin.

Norethisterone (NET) and its metabolite 5alpha-norethisterone (5alpha-NET) are competitors for the androgen receptor. The sensitivity of the rat vas deferens to the contractile action of methoxamine and serotonin is regulated by hormonal and anatomical factors. The aim of this study was to evaluate the ability of NET and 5alpha-NET to induce the androgen-regulated contractile response to methoxamine and serotonin in the epididymal and prostatic portions of rat vas deferens. Adult male rats either intact, castrated or steroid-treated castrated were used. The contractility was recorded isometrically, and non-cumulative concentration-response curves to either methoxamine or serotonin were obtained. NET and 5alpha-NET partially restored the sensitivity to methoxamine and serotonin in the epididymal portion of castrated rats. The maximal responses to both agonists were significantly higher than those observed in castrated rats, and significantly lower than the responses observed in either intact or androgen-treated castrated rats. The prostatic portion was less responsive to both agonists than the epididymal portion, in all groups but castrated rats, as castration induced sensitivity to both agonists. NET and 5alpha-NET displayed a partial though similar androgenic activity in the rat vas deferens. These results contrast with previous reports where a decrease of androgenic effect due to the 5alpha-reduction of NET has been found.     

Histochemical localization of ascorbic acid in the testis, epididymis and vas deferens of some rodents

Histochemical localization of ascorbic acid was carried out in the testis, epididymis and vas deferens of rat, guinea pig, mouse and also human beings, using a modified technique (CHINOY and SANJEEVAN 1978). The staining pattern was same in all cases, wherein, the nuclei were stained more intensely as compared to the cytoplasm. The luminal spermatozoa were also darkly stained. The significance of the localization is discussed in the light of the recent findings.     

Calcium antagonists and contractile responses in rat vas deferens and guinea pig ileal smooth muscle.

The effect of depletion of extracellular Ca2+ (Ca2+ext) on the loss of responsiveness of the guinea pig ileal longitudinal muscle (g.p.i.l.m.) and the rat vas deferens (r.v.d.) to K+ and cis-2-methyl-4-dimethylaminomethyl-1,3-dioxolane methiodide (CD), and K+ and noradrenaline (NA), has been examined and compared with the effects of a variety of local anesthetics and calcium antagonists. The results indicate that qualitative similarities are apparent with respect to the dependence of agonist-induced activity on Ca2+ext in both the g.p.i.l.m. and r.v.d. Distinct differences, however, in the Ca2+ translocation processes in these two tissues, in response to the different agonists, can be shown by the use of a variety of 'calcium antagonists' thus indicating that such translocation processes are both tissue and agonist selective. It is thus noted that, contrary to the Ca2+ depletion studies, D 600 and the usually more potent BAY-1040 showed no discrimination of action or potency in their ability to inhibit components of the NA response in the r.v.d. In contrast, D 600 and the more potent BAY-1040 selectively inhibited the tonic component of the K+ response. Treatment with SKF 525A and parethoxycaine (PC) in the g.p.i.l.m. and SKF 525A in the r.v.d. resulted in a nonselective inhibition of responses of the tissues to all stimulants. However, in the r.v.d. PC potentiated NA action, and its methobromide (MeBr) derivative potentiated both NA and K+ action and also, like PC, partially shifted to the left the dose-response curve to Ca2+ in NA-depolarizing Ca-free Tyrode's. The quaternary MeBr and the tertiary 2-chloroethyl (2Cl) derivatives of SKF 525A and PC were selectively more effective against CD- than K+ supported contractile activity in the g.p.i.l.m. and the 2Cl derivatives were more effective against NA than K+ responses in the r.v.d. The 2Cl derivative of PC also was more effective in antagonizing the Ca2+ dose-response curve in high-CD or high-NA than in high-K+ Ca2+-free Tyrode's.     

Influence of castration of the neonatal rat on the contractile effects of barium chloride and adrenaline in isolated vas deferens: the role of calcium

Time-response curves to maximal concentrations of barium chloride (BaCl2) (3 X 10(-2) M) and adrenaline (10(-4) M) were studied in vasa deferentia from 3-month-old rats castrated at birth. Either barium or adrenaline was left in the organ baths for 5-min periods, at intervals of about 30 min, and the corresponding isotonic contractions recorded. Two types of effects were measured: the fade response (Jurkiewicz et al., 1977) and the rate at which responses were reduced after Ca2+ withdrawal from nutrient solution. The fade response for BaCl2 was strikingly greater than that in controls. When calcium was removed from the nutrient solution, an almost complete loss of the response to BaCl2 was achieved in less than 3 min for preparations of 3-day castrates, in about 40 min for the organs of 15-day castrates, and in more than 140 min for normal preparations. Treatment with testosterone, 1 week before the experiments, abolished the fade response to BaCl2 and antagonized the loss of responsiveness observed for this substance in a calcium-deficient solution. These data suggest that the production of testosterone by the testis during the critical period of neonatal differentiation is important for the translocation of calcium ions in the isolated vas deferens of the adult rat.     

Involvement of calcium in calcium-current inactivation in smooth muscle cells from rat vas deferens

Summary Ca-channel currents were recorded in Cs-loaded single smooth muscle cells from rat vas deferens to define the dependence of the inactivation time course on Ca concentration. The decay of Ca-channel current obtained in a Ba²⁺- or Sr²⁺-containing external solution during long voltage-clamp pulses was much slower than that in a Ca-containing solution. The difference was not due to a change in the surface potential of the membrane as judged from the steady-state activation and inactivation curves. When Ca was the charge carrier, increasing external Ca concentration slightly accelerated the rate of inactivation. In addition, the rate of inactivation of Ca-channel current in 10.8mm Ba was also accelerated by adding Ca to the external solution in a concentration-dependent manner. The time course of Ca-current inactivation was slowed when the cells were dialyzed with a high concentration of citrate, a Ca-chelating agent. From these results, we concluded that a mechanism regulated by intracellular Ca activity plays a role in the inactivation of Ca channels in smooth muscle. The Ca-dependent process may protect against Ca overload by regulating Ca entry in smooth muscle cells.     

Effects of streptozotocin-induced diabetes and insulin on calcium responsiveness of the rat vas deferens

In the present study, effects of streptozotocin-induced diabetes and insulin treatment on the reactivity of rat vas deferens to KCl and calmidazolium, a calmodulin antagonist, were evaluated and calmodulin levels in vas deferens tissue from diabetic and insulin-treated rats were determined. Diabetes was induced in rats by a single injection of streptozotocin. Five weeks after the induction of diabetes, one group of diabetic rats was injected with insulin for 3 weeks. After 8 weeks, vas deferens tissues on one side of diabetic and insulin-treated diabetic rats and their controls were mounted in organ bath to measure isometric tension, while the tissues on the other side of rats were homogenized to determine calmodulin levels by radioimmunoassay. Concentration-response curves to KCl were obtained in vas deferens tissues in the absence and presence of calmidazolium. The effects of KCl and calmidazolium on vas deferens isolated from 8-weeks diabetic rats were decreased. Calmodulin levels were also found to be decreased in vas deferens from diabetic rats. Decreased calmodulin levels in diabetic rat vas deferens were not corrected by insulin treatment. Only a partial correction following insulin treatment was observed in contractile effect of KCl on diabetic rat vas deferens, whereas insulin treatment increases the affinity of calmodulin in this muscle. Experimental diabetes causes an impairment in calcium/calmodulin-dependent contractile process of vas deferens, which is correctable partially following insulin therapy. The changes in the function of rat vas deferens due to streptozotocin diabetes seem to be related to impaired sexual functions in human diabetes.     

Instantaneous reactions of guinea-pig vas deferens preparation to X-irradiation

Summary In the mechanical-inactive guinea-pig vas deferens X-rays (25 kV) at threshold doses of about 100 kR initiated phasic activity and an immediate increase in tone. After addition of acetylcholine, noradrenaline or adrenaline to the rinsing solution a slight contractile activity of vas deferens appeared and the preparation reacted to X-irradiation at a threshold dose of 3 to 5 kR (dose-rate 20 kR/min) with increased phasic contractions and with a dose and dose-rate dependent tonic contraction. After repeated irradiation a sensitization was observed. X-rays produced tonic contractions of the vas deferens preparation up to a total dose of about 200 kR (fractionated irradiation). An irreversible contraction of the vas appeared after continuous exposure to X-ray doses larger than 500 kR (dose-rate 20 kR/min).     

Structure and physiology of mammalian vas deferens in relation to fertility regulation

The structural and functional integrity of the vas deferens and its role in ensuring the fertilizing ability, viability of spermatozoa and their survival in the vas deferens, are elucidated. The regulation of the function of the vas deferens and the differential androgen dependency of its two regions have been discussed in relation to its secretory and absorptive activities as well as its contractility. The importance of ascorbic acid in maintaining its functions has also been investigated. The potentiality of the use of an androgen antagonist, steroids (testosterone, estradiol benzoate), prostaglandins, copper devices, vasectomy, vasocclusive agents, effects of nutr itional deficiencies, human chorionic gonadotropin-antiserum and plant products as antifertility agents have been discussed.     

Apparent low free magnesium levels in blue crab vas deferens determined by 31P NMR

• 1.1. ³¹P NMR examination of blue crab vas deferens reveals an α-β ATP chemical shift differences on average of 9.8 ppm.
• 2.2. This implies a free magnesium concentration well below 100 μM.
• 3.3. Thus crab vas deferens represents a new model for a low free magnesium system.
• 4.4. These results also point to a feature of carcine metabolism not previously recognized.