Increased contractility of diabetic rabbit corpora smooth muscle in response to endothelin is mediated via Rho-kinase beta.

Corpus cavernosum smooth muscle (CCSM) from rabbits made diabetic for 6 months as a result of alloxan injection exhibited increased sensitivity (3vs 9 nM EC(50)) and generated 20-50% greater force to endothelin-1 (ET-1) compared to CCSM from normal rabbits. In contrast, the force produced by the CCSM in response to KCl and phenylephrine was not significantly altered in diabetic CCSM. The increased ET-1 sensitivity is associated with a two to three-fold upregulation of ET receptor A at both mRNA and protein levels in diabetic CCSM. ET-1-induced CCSM contraction is largely dependent upon Rho-kinase (ROK), since it is almost completely blocked by Y-27632 (a highly selective ROK inhibitor). Furthermore, expression of ROKbeta isoform is selectively upregulated in CCSM from diabetic rabbits. Thus, an increased CCSM tone, modulated by sensitization of the endothelin-mediated contractile pathway via ROK, may be a key component of the molecular mechanism of diabetes-induced erectile dysfunction.

Regional variation in myosin isoforms and phosphorylation at the resting tone in urinary bladder smooth muscle.

Urinary bladder filling and emptying requires coordinated control of bladder body and urethral smooth muscles. Bladder dome, midbladder, base, and urethra showed significant differences in the percentage of 20-kDa myosin light chain (LC20) phosphorylation (35.45 +/- 4.6, 24.7 +/- 2.2, 13.6+/- 2.1, and 12.8 +/- 2.7%, respectively) in resting muscle. Agonist-mediated force was associated with a rise in LC20 phosphorylation, but the extent of phosphorylation at all levels of force was less for urethral than for bladder body smooth muscle. RT-PCR and quantitative competitive RT-PCR analyses of total RNA from bladder body and urethral smooth muscles revealed only a slight difference in myosin heavy chain mRNA copy number per total RNA, whereas mRNA copy numbers for NH2-terminal isoforms SM-B (inserted) and SM-A (noninserted) in these muscles showed a significant difference (2.28 x 10(8) vs. 1.68 x 10(8) for SM-B and 0.12 x 10(8) vs. 0.42 x 10(8) for SM-A, respectively), which was also evident at the protein level. The ratio of COOH-terminal isoforms SM2:SM1 in the urethra was moderately but significantly lower than that in other regions of the bladder body. A high degree of LC20 phosphorylation and SM-B in the bladder body may help to facilitate fast cross-bridge cycling and force generation required for rapid emptying, whereas a lower level of LC20 phosphorylation and the presence of a higher amount of SM-A in urethral smooth muscle may help to maintain the high basal tone of urethra, required for urinary continence.

Myosin light chain phosphorylation at resting level and the composition of myosin isoforms in the bladder body and urethra.

Bladder filling depends upon the coordinated control of a storage chamber, the bladder body, and its outlet, the bladder base and urethra. Bladder emptying results from development of force in the bladder body and relaxation of the outlet. Muscle strips from bladder body reveal phasic characteristics, whereas the strips from urethral wall are tonic. To determine whether the compositions of myosin heavy chain (MHC) isoforms and the level of myosin light chain (MLC) phosphorylation contribute to the regional variation in the contractile states of the bladder smooth muscle, we analyzed the levels of MLC phosphorylation and the expression of myosin isoforms in smooth muscle tissues from different regions of the urinary bladder. Strips of bladder from the dome, mid body, base of the bladder and urethra were removed and analyzed for the levels of MLC phosphorylation at the resting tone. The expression of MHC isoforms that differ in the C-terminus (SM1 and SM2) and in the N-terminal region (SM-A and SM-B), formed by alternative splicing of the pre-mRNA at either the 3' end or the 5' end, respectively, was analyzed. The expression of these isoforms was characterized at the mRNA and protein levels using reverse transcriptase-polymerase chain reaction (RT-PCR), SDS-PAGE, and Western blotting. The levels of MLC phosphorylation were 35.5 +/- 4.6, 24.7 +/- 2.2, 13.6 +/- 2.1, and 12.8 +/- 2.7 for dome, mid bladder body, base and urethra respectively. Almost 100% of the MHC mRNA in the dome, mid bladder body, and base contains a 7-amino acid insert near the ATP-binding region, whereas the MHC in the urethral smooth muscle is only 81% inserted. Prior studies have shown that inserted myosin has a two-fold higher actin-activated ATPase activity compared to the myosin isoform that lacks the insert, and the maximum velocity of shortening of smooth muscle containing this insert is high compared to muscle that do not contain the insert. The expression of SM1 and SM2 were not significantly different. Our data suggests the presence of a high degree of inserted myosin and LC20 phosphorylation in the bladder dome and mid-body helps to facilitate rapid force development and emptying. Non-inserted myosin and the low level of MLC phosphorylation in the urethra may contribute to slowly or non-cycling myosin cross bridges and the maintenance of a tonic or contracted state during bladder filling.

Evidence for a role of intracellular-calcium release in nitric oxide-stimulated relaxation of the rabbit corpus cavernosum.

Erection is mediated by relaxation of the smooth muscle elements within the sinusoids of the corpus cavernosum. Although cavernosal relaxation can be mediated by a variety of mechanisms including purinergic stimulation, prostoglandins, and beta-adrenergic stimulation the major mechanism involves the stimulated release of nitric oxide (NO) and subsequent relaxation of the corporal smooth muscle. Experimentally, NO can be released both by direct stimulation of NO-containing nerves (using field stimulation) and indirectly via cholinergic stimulation of NO release from the endothelium (using bethanechol). Preliminary studies have indicated that NO release and/or NO-stimulated relaxation of corporal smooth muscle is an active process involving both an increase in cytosolic calcium and an increase in metabolic energy utilization. Ryanodine is a pharmacological agent that can inhibit calcium-stimulated calcium release from the sarcoplasmic reticulum. The results of the current study demonstrated that ryanodine inhibited both field-stimulated relaxation and bethanechol-stimulated relaxation but did not affect relaxation induced by adenosine triphosphate (ATP) or nitroprusside. These studies strongly support the hypothesis that NO-stimulated relaxation is mediated, in part, by calcium release from the sarcoplasmic reticulum through ryanodine-sensitive channels.

Effect of partial outlet obstruction on 14C-adenine incorporation in the rabbit urinary bladder.

Bladder outlet obstruction induces severe changes in urinary bladder function and metabolism. These changes are characterized by significant reductions in the ability of the in vitro whole bladder to generate pressure and to empty. Metabolically, partial outlet obstruction induces a shift from oxidative to anaerobic metabolism. The decreased oxidative metabolism is mediated in part by significant decreases in mitochondrial substrate metabolism, which in turn is correlated with decreased activity of 2 important mitochondrial enzymes: citrate synthase and malate dehydrogenase. The present study was designed to evaluate mitochondrial function by studying the incorporation of 14C-adenine into high-energy phosphates (ATP, AMP, and ADP). Mild partial outlet obstructions were created by surgically placing silk ligatures loosely around the bladder neck. The results of these studies demonstrate that after 60 min incubation in oxygenated medium containing glucose + 1uCi14C-adenine, 1) There was no significant differences in the total AMP, ADP, and ATP concentrations measured in bladders taken from controls, 7- and 14-day obstructed rabbits; 2) there was no effect of obstruction on either the concentration of 14C-AMP in the tissue or in the ratio of hot to cold AMP; and 3) there was a 50% decrease in the concentration of 14C-ADP and a 70% decrease in the concentration of 14C-ATP in the bladder smooth muscle obtained from obstructed tissue (from both 7- and 14-day obstructions) compared to concentration in the control bladder smooth muscle. These results confirm the previous finding that obstruction did not reduce the rate of incorporation of adenine to AMP within the obstructed bladder smooth muscle and extends these studies to identify a significant reduction in the synthesis of both ADP and ATP. These results support the hypothesis that partial outlet obstruction induce a major dysfunction in mitochondrial function, both in the ability to oxidize substrates and in the ability to generate ATP.

Comparative response of rabbit bladder smooth muscle and mucosa to anoxia.

Recent studies indicate that the mucosa of the urinary bladder plays a major role in the maintenance of normal bladder function. Previous studies have demonstrated that rabbit bladder mucosa has higher rates of basal glycolysis and oxidative phosphorylation than that of bladder smooth muscle. The current study compares the response of rabbit bladder mucosa and smooth muscle compartments to anoxia. The results demonstrate that the rate of high energy phosphate degradation of the mucosa is significantly greater than the rate of high energy phosphate degradation of the smooth muscle. The implication is that the mucosa would be significantly more sensitive to ischemia than the smooth muscle of the bladder. This hypothesis may be extremely relevant to conditions such as interstitial cystitis and recurrent urinary bladder infections, in which ischemia has been implicated in their etiology.

Comparison of the pharmacological response of human corpus cavernosal tissue with the response of rabbit cavernosal tissue.

1. This study directly compares the response of cavernosal tissue obtained from sexually mature rabbits with the response of human corpus cavernosal tissue obtained during implant surgery for psychogenic impotence (five individual samples) to field stimulation and specific autonomic agonists. 2. At 2 g basal tension, field stimulation of the rabbit corpus cavernosal tissue produced a frequency dependent biphasic response consisting of an initial relaxation followed by contraction. Low frequency stimulation induced primarily relaxations whereas high frequency stimulation induced primarily contractions. FS of human corpus cavernosal tissue induced a frequency dependent contraction. 3. In general, the rabbit corpus cavernosal strips showed a significantly greater degree of spontaneous activity than the strips of human cavernosal tissue. 4. Phenylephrine stimulated a rapid and sustained increase in basal tension in both tissues. Although the isolated strips weighed the same, the magnitude of the response of the rabbit tissue was significantly greater than the response of the human tissue. 5. For both tissues, FS relaxations were completely inhibited by L-NAME showing that the relaxations were mediated by nitric oxide. Similarly, for both tissues, nitroprusside, ATP, and bethanechol induced similar dose-response relaxations of pre-stimulated tissue. 6. In conclusion, the major difference between the response of human and rabbit tissue to various forms of stimulation was that isolated strips of human corporal tissue responded to FS with contractions at all frequencies whereas the rabbit tissue responded to the relaxations at low frequencies of stimulation; a clear bi-phasic response at intermediate frequencies; and contraction at high frequencies.

Effect of magnesium ions on rabbit detrusor contractility and intracellular free calcium.

Magnesium (Mg2+) is one of the most abundant ions in the body. In the human body, Mg2+ plays important roles including cofactors in many crucial enzyme systems, especially those involving energy transfer, storage and utilization. Alteration of the concentration of Mg2+ may cause neuromuscular hyperactivity, psychiatric disturbances, calcium/potassium abnormalities, and overactivity of cardiac muscle. Most information on the effect of Mg2+ on muscle contraction has been obtained from studies on cardiac, skeletal, and vascular muscle; much less is known about the effect of Mg2+ in other smooth muscle systems. In the current study, we investigated the effect of Mg2+ on the contraction and intracellular free calcium of rabbit urinary bladder detrusor muscle in response to carbachol and transmural field stimulation (FS). The results can be summarized as follows: (1) Reduction of the concentration of magnesium [Mg2+] from normal Tyrode's solution enhanced the spontaneous basal activity, whereas addition of Mg2+ gradually abolished this spontaneous activity. (2) Muscle contraction induced by FS or carbachol was enhanced in Mg(2+)-free Tyrode's solution. Addition of Mg2+ inhibited the response to both forms of stimulation in a dose-dependent manner. (3) Inhibitory effects of Mg2+ were potentiated when the Ca2+ concentration in the Tyrode's solution was reduced to 0.6 mM, whereas increasing the extracellular concentration of Ca2+ (5.4 mM) reduced the inhibitory effects of Mg2+. (4) Using FURA-2 to monitor intracellular free calcium simultaneous with contractile tension, we demonstrated that the alterations in the contractile responses observed at different concentrations of extracellular Mg2+ correlated with similar changes in intracellular free calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic responses of rabbit corpus cavernosum tissue to various forms of stimulation.

The present study was designed to investigate the effect of various forms of stimulation on the levels of high energy phosphates (ATP + CP) in the rabbit corpora cavernosa. Prestimulation with the alpha agonist phenylephrine (200 microM) for five minutes caused a significant decrease in both ATP and Creatine phosphate (CP) when compared with control tissue. Field stimulation (64 Hz) of the precontracted tissue induced an immediate decrease in tension by approximately 50%. The level of ATP + CP after field stimulated-relaxation was not significantly different from that from the initial prestimulation. Field stimulation (FS) from basal tone (2 g) caused a contraction and a significant decrease in both ATP and CP. Phentolamine (10 microM) (alpha-adrenergic antagonist) induced a significant decrease in the 2 g basal tension and a significant increase in the intracellular concentrations of both ATP and CP from that of control levels. In summary, the contractile response to both neuronal and pharmacologic stimulation was similar to that of other smooth muscle, producing a decrease in high energy phosphates. Field stimulated relaxation did not change the level of high energy phosphates from that of prestimulated levels. Finally, our data indicates that in the presence of the alpha blocker phentolamine (10 microM), high energy phosphate levels (ATP + CP) increase significantly. This indicates that in the corpus cavernosum, there is significant basal tone that is linked to significant tonic alpha receptor stimulation and is maintained by a net consumption of ATP.

Pharmacological effect of ethanol on the function of rabbit corporal cavernosal tissue.

Pharmacologic and behavioral effects of alcohol on male sexual activity have long been controversial. Among the varied effects of alcohol, it has been described that ethanol reduces nitric oxide production. Appreciating the importance of nitric oxide-mediated regulation of corporal smooth muscle, this study was designed to investigate the in vitro pharmacologic effect of 1-5% ethanol on rabbit corpus cavernosum function. The results are summarized as follows. In isolated organ bath experiments, basal resting tension of corporal strips was significantly reduced with 3 and 5% ethanol exposure. Relaxation induced by field stimulation over a frequency range of 2-16 Hz was significantly decreased with 3 and 5% ethanol exposure. However, field-stimulated contraction at 32 Hz was reduced by 5% ethanol only. When corporal strips were preincubated with phenylephrine, 3 and 5% ethanol significantly inhibited field stimulated relaxation at all frequencies. Both phasic and tonic contraction induced by phenylephrine was significantly suppressed by 3 and 5% ethanol. KCl-induced contraction was decreased by 5% ethanol. ATP-induced relaxation was significantly enhanced by 1, 3 and 5% ethanol. Bethanechol-induced relaxation was significantly suppressed by 1, 3 and 5% ethanol. Direct nitroprusside-induced relaxation was not affected by any concentration of ethanol administration. These results demonstrated that ethanol had significant effects on both contraction and relaxation of rabbit corpus cavernosum. In general, corporal relaxation mediated through the acetylcholine-L-arginine-nitric oxide pathway was significantly more sensitive to ethanol than either ATP- or nitroprusside-induced relaxation.

Effect of partial outflow obstruction on rat detrusor contractility and intracellular free calcium concentration.

Partial outlet obstruction induces significant alteration in detrusor contractility. A mild obstruction can result in increased contractile force, whereas severe obstruction results in marked contractile dysfunction. The cellular mechanisms mediating these alterations in the contractile response are presently not known. In the current study, we have investigated the effect of both mild and severe partial outlet obstruction on detrusor contractility and correlated the contractile response to field stimulation, bethanechol, adenosine triphosphate (ATP), and KCl with the level of intracellular free calcium using FURA-2 fluorescence. Our results are as follows. Severe obstruction induced a significantly greater increase in bladder weight than mild obstruction. In general, mild outlet obstruction induced an increase in the contractile responses to field stimulation, bethanechol, ATP, and KCl, whereas severe outlet obstruction induced a decrease to field stimulation and ATP. In general, the stimulated increase in intracellular free calcium paralleled the contractile response. The results indicate that the alterations in the contractile response to field stimulation and pharmacological stimulation induced by partial outlet obstruction may be mediated by altered calcium translocation and intracellular release.

Metabolic studies on the rabbit corpus cavernosum.

Erectile function (erection and detumescence) involves the complex interaction of direct neuronal stimulation of corporal smooth muscle, neurohumoral release of specific endothelial contractile and relaxant factors, and secondary modulation by a variety of putative neuropeptides and vasoactive modulators. The net result is a rapid and sustained relaxation of the smooth muscle elements during erection and contraction of the smooth muscle during detumescence. Proper function of the corporal tissue is dependent upon cellular metabolism of glucose and the generation of cellular energy in the form of high energy phosphates. The current study characterizes the following metabolic parameters of the rabbit corpus cavernosum: Tissue concentrations of creatine phosphate (CP), ATP, ADP, and AMP; maximal rate of glucose metabolism to lactic acid and CO2; and activities of the enzymes creatine kinase (CK), citrate synthase, and malate dehydrogenase. For comparative purposes only, bladder smooth muscle preparations were analyzed simultaneously with and under the same conditions as the corpus cavernosum. The results are as follows: The concentrations of ATP and CP in the corpora were significantly lower than the concentrations in bladder. In the corpora, the tissue concentration of CP was lower than the tissue concentration of ATP, whereas the concentration of CP in the bladder was higher than the concentration of ATP. The rate of glucose metabolism to lactic acid and to carbon dioxide was similar for both bladder smooth muscle and corpus cavernosum. The maximal enzymatic activity of the mitochondrial enzyme citrate synthase was similar for both tissues; similarly, there was no significant difference in the activity of malate dehydrogenase between the two tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of purines on rabbit corpus cavernosum contractile activity.

At least three well documented neuropharmacologic mediators participate in physiologic erection: inhibition or cessation of alpha-adrenergic transmission, increases in both cholinergic (acetylcholine) and non-adrenergic non-cholinergic (NANC) transmission. In-vitro studies of rabbit corporal smooth muscle reveal that adenosine tri-phosphate (ATP) has a variable effect on muscle tension depending on the level of basal tone. ATP has a pronounced relaxant effect on corporal smooth muscle at either high basal tension or pre-stimulated tension. ATP stimulates a contraction in corporal smooth muscle at low tension. The current studies compare the effects of a series of purines (adenine, adenosine, AMP, ADP, ATP and beta-gamma methylene ATP) on both basal tension and on field-stimulated relaxation. The results demonstrate that all purines relax both baseline tension (2g) and phenylephrine-stimulated contraction. Following phenylephrine pre-stimulation: beta-gamma methylene ATP was significantly more potent than ATP at inhibiting tension. ADP, AMP, adenosine, and adenine produced intermediate dose-response relaxation curves. At 2 grams baseline tension, adenosine, ADP, and AMP were equally potent relaxing agents, ATP was slightly less potent. Adenine and beta-gamma-methylene ATP induced similar dose-response curves which were significantly less potent and efficacious than adenosine, AMP, ADP, and ATP. Field stimulation of phenylephrine pre-contracted tissue strips produce relaxation at both low and high frequencies. None of the purines either facilitated or inhibited the corporal response to field stimulation. We conclude that field stimulated relaxation of rabbit corporal smooth muscle is independent of purinergic relaxation.

Metabolic studies on rabbit bladder smooth muscle and mucosa.

Recent studies indicate that the mucosa of the urinary bladder may play a major role in the maintenance of normal bladder function. The mucosal surface of the urinary bladder serves as a protective layer against the irritative solutes found in the urine. The integrity of this barrier can be broken by overdistension, anoxia, detergents, alcohols, bacterial infection and by contact with agents to which the mucosa has been sensitized. In view that both anoxia and ischemia can mediate a breakdown in the role of the mucosal layer as a permeability barrier, it is reasonable to assume that this function is dependent on cellular metabolism. As an initial investigation we have compared a variety of biochemical and metabolic parameters between the mucosal layer (consisting of the lamina propria, urothelium, and any connective tissue and vascular tissue within this layer); and the muscularis layer. The results of these studies demonstrated that the rate of glucose metabolism to lactic acid (LA) of the mucosa was more than three-fold greater than that of the smooth muscle. The rate of CO2 production of the mucosa was 60% greater than that of the unstimulated smooth muscle. The maximal activity of the mitochondrial enzyme citrate synthase was significantly greater in the mucosa than in the smooth muscle, however, the activity of malate dehydrogenase was similar for both tissues. The maximal activity of the cytosolic enzyme creatine kinase was more than two-fold greater in the bladder smooth muscle than in the mucosa; although the affinities of the creatine kinase isoforms of the mucosa were significantly greater than those of the muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation of contractile function of the rabbit corpus cavernosum with NADH fluorescence.

The NADH/NAD ratio is a measure of potential metabolic energy in smooth muscle tissue. Previous studies on bladder smooth muscle demonstrated that during active contraction when energy utilization is high, NADH is rapidly oxidized to NAD resulting in a decrease in the ratio of NADH/NAD. Intracellular systems utilizing ATP as an energy source are characterized by changes in the NADH/NAD ratio. This ratio can be monitored simultaneously with changes in smooth muscle tissue tone using an optical fiber probe which continually monitors NADH fluorescence and contractile activity of the same smooth muscle preparation. The present study correlates alterations in the ratio of NADH/NAD with both spontaneous and induced contractions and relaxations in the rabbit corpora cavernosa. The results show a high degree of correlation between a decrease in spontaneous fluorescence (decrease in the NADH/NAD ratio) and spontaneous contraction. An increase in tension was followed in time by a decrease in the NADH/NAD ratio. This was consistent for all strips showing significant spontaneous activity. ATP caused a rapid decrease in tension which was correlated with a decrease in fluorescence. The relative decrease in NADH fluorescence was proportional to the relative decrease in tension. Under basal conditions (0.8 g passive tension) ATP and nitroprusside stimulated a marked reduction in tension, but only ATP stimulated a substantial decrease in NADH fluorescence. Bethanechol and isoproterenol relaxed the corporal tissue to a relatively small degree which correlated with relatively small decreases in fluorescence. Methoxamine stimulated a substantial contraction of corporal smooth muscle which correlated with a rapid and significant decrease in NADH fluorescence.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of substrates in the maintenance of contractility of the rabbit urinary bladder.

Recent studies have shown that muscarinic stimulation causes an increase in the breakdown of glucose and glycogen leading to an increase in lactate and CO2 production and a decrease in the ratio of NADH/NAD. Similar studies using palmitate as substrate showed that bethanechol did not change the rate of palmitate oxidation. Using both isolated strips of rabbit bladder dome, and the rabbit in vitro whole-bladder model, the present study compares the ability of glucose, pyruvate, palmitate, succinate and malate to support contraction and correlates the results with the intracellular concentration of high-energy phosphates. The results can be summarized as follows. In the absence of substrate, the peak response of muscle strips to field stimulation (32 Hz, 80 V, 1 ms) decreased progressively with time to 85% of the initial response at 60 min and 72% at 160 min. In contrast, the plateau phase of the response decreased to 45 and 23% of the initial response at 60 and 160 min, respectively. When glucose was present in the incubation medium, the peak and plateau tensions were 86 and 73% of the initial values at 160 min. Similar experiments with pyruvate as substrate showed that at 160 min both peak and plateau were elevated above initial values (peak = 119%; plateau = 123%). In the presence of palmitate, succinate or malate, the peak and plateau tensions decreased with time at a similar rate as in the absence of substrate. The reduction in tissue content of pre-formed high energy phosphates was similar for zero substrate and when palmitate, succinate or malate were present in the bath.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissociation of the metabolic from the contractile response to muscarinic stimulation in the rabbit urinary bladder.

The calcium dependence of contraction and NADH fluorescence was investigated in rabbit bladder stimulated with bethanechol or KCl. The absence of calcium in the bathing solution induced a rightward shift in the dose response to bethanechol for both contraction and NADH fluorescence. The contractile response was shifted to a greater degree than the fluorescence response and the maximal response to bethanechol was reduced by 80% for contraction but only 20% for NADH fluorescence. This rightward shift was also induced by the benzothiazepine calcium antagonist diltiazem (200 microM) and again the contractile response was shifted significantly more than the fluorescence response. The combination of zero calcium and 200 microM diltiazem virtually abolished contractions but only inhibited the NADH fluorescence by 65% at maximally effective bethanechol concentrations. Unlike the effect of diltiazem on the response to bethanechol, diltiazem (200 microM) shifted both the contraction and fluorescence curves to the right equally in response to KCl stimulation. These results indicate that a metabolic response to muscarinic stimulation (decreased NADH) can occur in the absence of any observable contractile response. This metabolic response may be due to post receptor signal processing events. For KCl stimulation, the NADH response is probably secondary to and a result of the contractile response.

Clinical use of the turbidimetric analysis of sperm motility: an update.

The turbidimetric method of sperm motility analysis provides a quantitative measure of sperm motility. We have previously reported the methodology by which this method is utilized in routine sperm motility determinations in our Male Fertility Clinic. We have recently observed that the motility of sperm in dialyzed seminal plasma is over double the motility in Lopata's medium. This report provides quantitative evidence that the use of dialyzed seminal plasma in the turbidimetric analysis is significantly superior than the use of Lopata's medium.