The impact of rational pharmacotherapy training reinforced via prescription audit on the prescribing skills of fifth-year medical students.

OBJECTIVE: The aim of the study was to demonstrate the impact of a rational pharmacotherapy (RPT) clerkship reinforced via prescription audit (PA) on the prescribing skills of fifth-year medical students trained by both pharmacologists and clinicians at Gazi University Medical School. METHODS: The RPT training lasted for five days. A total of 101 medical students were included in the study. The students were asked to prescribe for standardized patients with uncomplicated essential hypertension. PA was performed on the prescriptions on the first (PA1) and last (PA2) days of the clerkship to determine the influence of the clerkship on the prescribing habits. The students were also asked to comment on PA with a short questionnaire at the end of the clerkship. The difference between PA scores was analyzed using the Mann-Whitney-Rank-Sum-test. RESULTS: Scores for PA1 and PA2 and the feedback of the medical students were compared. A significant improvement in PA scores was observed by the end of the clerkship. The commonest drugs in the prescriptions in both PA1 and PA2 were angiotensin-converting enzyme (ACE) inhibitors. The feedback from the medical students revealed that PA improved their prescription skills and that the trainers helped them to reach the targets, helped them to gain self-confidence and they agreed that PA should be applied in clinical pharmacology courses. CONCLUSIONS: RPT training reinforced via PA guided by clinicians and pharmacologists is helpful in improving the prescribing skills of medical students. ACE inhibitors were the commonest group of drugs chosen by the medical students both before and after the clerkship. Prescription audit together with the clerkship caused a significant improvement in all parts of the prescription determined by prescription audit. The cooperation of pharmacologists and clinicians helped the clerkship to reach the targets.

Effect of melatonin and time of administration on irradiation-induced damage to rat testes.

The effect of ionizing irradiation on testes and the protective effects of melatonin were investigated by immunohistochemical and electron microscopic methods. Eighty-two adult male Wistar rats were divided into 10 groups. The rats in the irradiated groups were exposed to a sublethal irradiation dose of 8 Gy, either to the total body or abdominopelvic region using a 60Co source at a focus of 80 cm away from the skin in the morning or evening together with vehicle (20% ethanol) or melatonin administered 24 h before (10 mg/kg), immediately before (20 mg/kg) and 24 h after irradiation (10 mg/kg), all ip. Caspace-3 immunoreactivity was increased in the irradiated group compared to control (P < 0.05). Melatonin-treated groups showed less apoptosis as indicated by a considerable decrease in caspace-3 immunoreactivity (P < 0.05). Electron microscopic examination showed that all spermatogenic cells, especially primary spermatocytes, displayed prominent degeneration in the groups submitted to total body and abdominopelvic irradiation. However, melatonin administration considerably inhibited these degenerative changes, especially in rats who received abdominopelvic irradiation. Total body and abdominopelvic irradiation induced identical apoptosis and testicular damage. Chronobiological assessment revealed that biologic rhythm does not alter the inductive effect of irradiation. These data indicate that melatonin protects against total body and abdominopelvic irradiation. Melatonin was more effective in the evening abdominopelvic irradiation and melatonin-treated group than in the total body irradiation and melatonin-treated group.

Effect of melatonin and time of administration on irradiation-induced damage to rat testes

The effect of ionizing irradiation on testes and the protective effects of melatonin were investigated by immunohistochemical and electron microscopic methods. Eighty-two adult male Wistar rats were divided into 10 groups. The rats in the irradiated groups were exposed to a sublethal irradiation dose of 8 Gy, either to the total body or abdominopelvic region using a 60Co source at a focus of 80 cm away from the skin in the morning or evening together with vehicle (20% ethanol) or melatonin administered 24 h before (10 mg/kg), immediately before (20 mg/kg) and 24 h after irradiation (10 mg/kg), all ip. Caspace-3 immunoreactivity was increased in the irradiated group compared to control (P < 0.05). Melatonin-treated groups showed less apoptosis as indicated by a considerable decrease in caspace-3 immunoreactivity (P < 0.05). Electron microscopic examination showed that all spermatogenic cells, especially primary spermatocytes, displayed prominent degeneration in the groups submitted to total body and abdominopelvic irradiation. However, melatonin administration considerably inhibited these degenerative changes, especially in rats who received abdominopelvic irradiation. Total body and abdominopelvic irradiation induced identical apoptosis and testicular damage. Chronobiological assessment revealed that biologic rhythm does not alter the inductive effect of irradiation. These data indicate that melatonin protects against total body and abdominopelvic irradiation. Melatonin was more effective in the evening abdominopelvic irradiation and melatonin-treated group than in the total body irradiation and melatonin-treated group.

The effect of experimental diabetes on the circadian pattern of adenosine deaminase and myeloperoxidase activities in rat liver.

This study investigated time-dependent variations in the activities of adenosine deaminase (ADA), an adenosine-metabolizing enzyme, and myeloperoxidase (MPO), an oxidation reaction-catalyzing enzyme, in control and streptozotocin (STZ)-induced diabetic rat liver. The animals were sacrificed at six different times of day (1, 5, 9, 13, 17 and 21 hours after lights on - HALO). The hepatic activity of ADA did not change depending on the STZ treatment whereas MPO activity was significantly higher in the diabetics than in the controls. Hepatic ADA activity was dependent on the time of sacrifice with the lowest activity at 21 HALO and the highest activity at 5 HALO. Both enzyme activities failed to show any significant interaction between STZ treatment and time of sacrifice, which means that diabetes does not influence the 24 h pattern of these activities. Since MPO, a heme protein localized in the leukocytes, is involved in the killing of microorganisms, increased MPO activity in diabetic rat liver may reflect leukocyte infiltration secondary to diabetes. A reduction in ADA activity during the dark (activity/feeding) period will presumably lead to high concentrations of adenosine in the liver, possibly contributing to changes in some metabolic processes, such as glycogen turnover and oxygen supply.

The effect of experimental diabetes on the twenty-four-hour pattern of the vasodilator responses to acetylcholine and isoprenaline in the rat aorta.

The aim of this study was to investigate whether time-dependent variations in the relaxant effect of acetylcholine, an endothelium-dependent vasorelaxant via muscarinic receptors, and isoprenaline, a nonselective beta-adrenoceptor agonist in rat aorta, are influenced by streptozotocin (STZ)-induced experimental diabetes. Adult male rats were divided randomly into two groups: control and STZ-induced (STZ, 55 mg/kg, intraperitoneal) diabetes. The animals were synchronized to a 12:12 h light-dark cycle (lights on 08:00 h) and sacrificed at six different times of day (1, 5, 9, 13, 17, and 21 hours after lights on; HALO) eight weeks after STZ injection. The in vitro responsiveness of thoracic aorta rings obtained from control and diabetic rats to acetylcholine (10(-9)-10(-5) M) and isoprenaline (10(-10)-10(-3) M) was determined in six different times. EC(50) (the concentration inducing half of the maximum response) values and maximum responses were calculated from cumulative concentration-response curves of the agonists and were analyzed with respect to time and STZ treatment. Treatment, time, and interactions between treatment and time were tested by two-way analysis of variance (ANOVA). To analyze differences due to biological time, one-way ANOVA was used. STZ treatment did not significantly change EC(50) values or maximum responses for both agonists. There were statistically significant time-dependent variations in the EC(50) values for isoprenaline and maximum responses for both acetylcholine and isoprenaline in control groups by one-way ANOVA, but significant time-dependent variations disappeared in the aortas isolated from STZ-induced diabetic rats. The vasodilator responses to acetylcholine and isoprenaline failed to show any significant interaction (treatmentxtime of study) between STZ treatment and time of sacrifice in both EC(50) values and maximum responses by two-way ANOVA. These results indicate there is a basic temporal pattern in the responses to acetylcholine and isoprenaline in rat aorta which continues in diabetes. It is shown for the first time that experimental diabetes does not change the 24 h pattern of responses to acetylcholine and isoprenaline, and that time-dependent variations in the responses to these agonists disappear in diabetic animals. Although further studies are required to define the underlying mechanism(s) of these findings, results suggest that experimental diabetes can modify the time-dependent vasorelaxant responses of rat aorta. This may help to understand the circadian rhythms in cardiovascular physiology and pathology or in drug effects in diabetes.

Melatonin prevents inflammation and oxidative stress caused by abdominopelvic and total body irradiation of rat small intestine

We investigated the day-night differences in intestinal oxidative-injury and the inflammatory response following total body (TB) or abdominopelvic (AP) irradiation, and the influence of melatonin administration on tissue injury induced by radiation. Rats (male Wistar, weighing 220-280 g) in the irradiated groups were exposed to a dose of 8 Gy to the TB or AP region in the morning (resting period - 1 h after light onset) or evening (activity span - 13 h after light onset). Vehicle or melatonin was administered immediately before, immediately after and 24 h after irradiation (10, 2.0 and 10 mg/kg, ip, respectively) to the irradiated rats. AP (P < 0.05) and TB (P < 0.05) irradiation applied in the morning caused a significant increase in thiobarbituric acid reactive substance (TBARS) levels. Melatonin treatment in the morning (P < 0.05) or evening (P < 0.05) decreased TBARS levels after TB irradiation. After AP irradiation, melatonin treatment only in the morning caused a significant decrease in TBARS levels (P < 0.05). Although we have confirmed the development of inflammation after radiotherapy by histological findings, neither AP nor TB irradiation caused any marked changes in myeloperoxidase activity in the morning or evening. Our results indicate that oxidative damage is more prominent in rats receiving TB and AP irradiation in the morning and melatonin appears to have beneficial effects on oxidative damage irrespective of the time of administration. Increased neutrophil accumulation indicates that melatonin administration exerts a protective effect on AP irradiation-induced tissue oxidative injury, especially in the morning.

Melatonin prevents inflammation and oxidative stress caused by abdominopelvic and total body irradiation of rat small intestine.

We investigated the day-night differences in intestinal oxidative-injury and the inflammatory response following total body (TB) or abdominopelvic (AP) irradiation, and the influence of melatonin administration on tissue injury induced by radiation. Rats (male Wistar, weighing 220-280 g) in the irradiated groups were exposed to a dose of 8 Gy to the TB or AP region in the morning (resting period - 1 h after light onset) or evening (activity span - 13 h after light onset). Vehicle or melatonin was administered immediately before, immediately after and 24 h after irradiation (10, 2.0 and 10 mg/kg, ip, respectively) to the irradiated rats. AP (P < 0.05) and TB (P < 0.05) irradiation applied in the morning caused a significant increase in thiobarbituric acid reactive substance (TBARS) levels. Melatonin treatment in the morning (P < 0.05) or evening (P < 0.05) decreased TBARS levels after TB irradiation. After AP irradiation, melatonin treatment only in the morning caused a significant decrease in TBARS levels (P < 0.05). Although we have confirmed the development of inflammation after radiotherapy by histological findings, neither AP nor TB irradiation caused any marked changes in myeloperoxidase activity in the morning or evening. Our results indicate that oxidative damage is more prominent in rats receiving TB and AP irradiation in the morning and melatonin appears to have beneficial effects on oxidative damage irrespective of the time of administration. Increased neutrophil accumulation indicates that melatonin administration exerts a protective effect on AP irradiation-induced tissue oxidative injury, especially in the morning.

Circadian variations in the activities of 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase in the liver of control and streptozotocin-induced diabetic rats.

The aim of this study was to examine: the 24 h variation of 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase activities, key enzymes for the maintenance of intracellular NADPH concentration, in rat liver in control and streptozotocin-induced diabetic animals. Adult male rats were fed ad libitum and synchronized on a 12:12 h light-dark cycle (lights on 08:00 h). One group of animals was treated with streptozotocin (STZ, 55 mg/kg, intraperitoneal) to induce experimental diabetes. Eight weeks after STZ injection, the animals were sacrificed at six different times of day--1, 5, 9, 13, 17 and 21 Hours After Lights On (HALO)--and livers were obtained. Enzyme activities were determined spectrophotometrically in triplicate in liver homogenates and expressed as units per mg protein. 6-phosphogluconate dehydrogenase activity was measured by substituting 6-phosphogluconate as substrate. Glucose-6-phosphate dehydrogenase activity was determined by monitoring NADPH production. Treatment, circadian time, and interaction between treatment and circadian time factors were tested by either one or two way analysis of variance (ANOVA). Two-way ANOVA revealed that 6-phosphogluconate dehydrogenase activity significantly depended on both the treatment and time of sacrifice. 6-phosphogluconate dehydrogenase activity was higher in control than diabetic animals; whereas, glucose-6-phosphate dehydrogenase activity did not vary over the 24 h in animals made diabetic by STZ treatment. Circadian variation in the activity of 6-phosphogluconate dehydrogenase was also detected in both the control and STZ treatment groups (one-way ANOVA). Time-dependent variation in glucose-6-phosphate dehydrogenase activity during the 24 h was detected in control but not in diabetic rats. No significant interaction was detected between STZ-treatment and time of sacrifice for both hepatic enzyme activities. These results suggest that the activities of NADPH-generating enzymes exhibit 24 h variation, which is not influenced by diabetes.

Comparison of different de-endothelization procedures in the isolated rat thoracic aorta: a short communication.

The aim of this study was to compare the effects of different techniques used for deendothelization on responses to endothelium-dependent (acetylcholine) and -independent (sodium nitroprusside) vasodilators and vasoconstrictor (phenylephrine) in the isolated rat thoracic aorta. Four different methods were used for de-endothelization: (1) mechanical (wire), (2) physical (distilled water), (3) chemical (Triton X-100 and saponin) and (4) enzymatic (trypsin). The results showed that mechanical rubbing with rough-surfaced wire was the most effective procedure amongst five different techniques used for deendothelization in the isolated rat thoracic rings. Denudation by wire abolished endothelium-dependent relaxation successfully without much interfering smooth muscle vasodilating and contracting properties of the agonists. It seems that physical, chemical and enzymatic techniques are not suitable for endothelial denudation in the isolated thoracic rat aorta preparations. These endothelium removing methods may be useful for studying the role of endothelium in vascular beds or small diameter vessels whose endothelial cells can not be removed mechanically.

The role of tumour necrosis factor-alpha (TNF-alpha) and platelet-activating factor (PAF) interaction on murine candidosis.

Tumour necrosis factor-alpha (TNF-alpha) is related to some other factors in addition to being the essential cytokine of the sepsis which results from Candida infections. In our study, we investigated serum TNF-alpha levels, measured by enzyme-linked immunosorbent assay (ELISA), and platelet-activating factor (PAF)-like activity, measured by high-pressure liquid chromatography (HPLC) of the mice infected with Candida species. The PAF antagonist, ginkgolide BN 52021 was used to evaluate the possible interaction between TNF-alpha and PAF. The average TNF-alpha levels were found to be 396, 489, 699 and 803 pg ml(-1) on the 4th, 5th, 6th and 19th days of Candida albicans infection, respectively (P<0.05). There was no statistically significant difference between the serum TNF-alpha levels of the groups infected with other Candida species, such as C. kefyr, C. krusei and C. tropicalis (P>0.05). Serum TNF-alpha levels were found to be more significantly different in mice with C. albicans infection that were injected with PAF antagonists on the 6th day (23 pg ml(-1)). It was therefore thought that PAF antagonists have an inhibitory effect on TNF-alpha production. No significant difference was found between PAF levels in the three groups: healthy control mice, C. albicans-infected mice and C. albicans-infected mice given PAF antagonists (466 milli-absorbance unit (mAU), 475 mAU and 329 mAU, respectively). It was noticed that the positive interaction between PAF and TNF-alpha was not important after the first 4 days of the infection had passed.

Biological-time-dependent differences in effect of verapamil on rat aorta and influence of endothelium.

The biological-time-dependent variation in the vasodilator effect of verapamil on rat thoracic aorta was assessed in both endothelium-intact and denuded preparations. Groups of adult male rats were housed in light from 08:00 to 20:00 and in darkness from 20:00 to 08:00 and sacrificed at six different times of the day (1, 5, 9, 13, 17, and 21 hours after lights on; HALO). Verapamil caused concentration-dependent relaxations in both endothelium-intact and denuded aortic rings precontracted with phenylephrine (Phe). In endothelium-intact rings, neither the AUC nor the EC50 values for verapamil exhibited significant biological-time-dependent effects, as determined by one-way analysis of variance (ANOVA). In endothelium-denuded rings, AUC values did vary in a statistically significant manner according to the biological time of study, while the EC50 values did not. Endothelium denudation led to an increase in EC50 values at almost every time point. Statistically significant interactions between the biological time of study and treatment (intact vs. denuded endothelium) in both AUC and EC50 values were documented by two-way ANOVA; this indicated differences in the clock-time staging of verapamil-induced relaxation in endothelium-denuded versus intact aortic rings.

Endothelium-dependent vasodilation in the isolated rabbit kidney following in vivo and in vitro ischaemia and reperfusion: effects of antagonizing platelet activating factor (PAF).

Renal ischaemia-reperfusion (I/R) is a pathological condition occurring frequently after transplantation and acute renal failure. A mediator thought to play a role in the disturbed haemodynamics of I/R is platelet activating factor (PAF). We studied endothelium-dependent (acetylcholine, ACh) and -independent (sodium nitroprusside, SNP) vasorelaxant responses and the effect of BN 52021, a PAF antagonist, in the isolated perfused rabbit kidney after in vivo and in vitro I/R. Anaesthetized rabbits underwent right nephrectomy and 1 h left renal artery clamping followed by 30min reperfusion with blood. In another group, kidneys were isolated and, after transferral to the perfusion system, the perfusion pump was turned off for 1 h, followed by 30min reperfusion with Krebs' solution. BN 52021 or its vehicle dimethylsulphoxide (DMSO) was administered 20min before left renal artery occlusion or turning off the pump. Although in vitro I/R did not influence ACh-induced responses, in vivo I/R caused a decrease which was prevented by BN 52021. SNP-induced responses did not change in in vitro I/R and decreased only at lower concentrations in in vivo I/R, whereby pretreatment with BN 52021 did not offer any protection. It is concluded that in vivo I/R diminishes ACh-induced endothelium-dependent vasodilation, possibly via PAF and blood components, whereas SNP-induced endothelium-independent vasodilation was not altered by in vivo and in vitro ischaemia in the isolated rabbit kidney.

Temporal variation in serum nitrite levels in rats and mice.

Although considerable evidence implicates involvement of nitric oxide (NO) in circadian regulation, little is known about possible 24 h variations in basal NO metabolism. In this study, daily variations in serum nitrite levels were studied in locally bred mice and rats during the months of September and October. The serum was separated from blood samples obtained at six different times of the day and night (1 h, 5 h, 9 h, 13 h, 17 h, and 21 h after lights off [HALO] from male albino mice and rats). As an index of in vivo NO generation, serum nitrite levels (determined by the diazotization method) in rats exhibited significant temporal fluctuation (unpaired Student t test), with the concentration highest at 5 HALO and 21 HALO and lowest at 9 HALO. No such temporal variation was detected in mice in these studies conducted on locally bred animals in the autumn.

Intermediate dose of methotrexate toxicity in non-Hodgkin lymphoma.

Methotrexate (MTX) is the chemotherapeutic for which the serum levels can be detected. If the MTX level is detected in time, high toxicity risk can be decreased. In this study, intermediate doses of MTX (1 g/m2) infusions are administered to B-cell non-Hodgkin lymphoma patients between 3 and 13 years old. The toxicity of MTX in accordance with serum levels and the toxicity of other combined drugs are investigated. Blood samples were collected consecutively, and MTX levels were detected by high-performance liquid chromatography. When hematological, gastrointestinal, and renal toxicity scores were compared with the 24-h serum levels of MTX, they showed a significant positive correlation. Hematological toxicity scores increased by Ifosfamide, Etoposide, and Cytarabine combined with MTX without altering the serum levels. Antibiotic combination with MTX has no effect on the toxicity scores. In conclusion, if MTX is combined with other myelosuppressive, hepatotoxic, and nephrotoxic drugs, the measurement of MTX serum levels alone is not a sufficient parameter to show the toxicity.

In vitro susceptibility rhythms. II. Biological-time-dependent differences in effect of beta 1- and beta 2-adrenergic agonists of rat aorta and influence of endothelium.

Time-dependent variations in the vasodilator effects of beta-adrenergic agonists terbutaline (Ter) and dobutamine (Dob) were studied in isolated rings of rat thoracic aorta in both endothelium-intact and endothelium-denuded preparations. Rats were housed in light from 08:00 to 20:00 and in darkness from 20:00 to 08:00 and sacrificed at six different times of the day. In endothelium-intact and endothelium-denuded aortic rings precontracted submaximally with phenylephrine (Phe), addition of Ter and Dob produced concentration-dependent relaxations. Removal of endothelium reduced the relaxant responses and area under curve (AUC) values and augmented the EC50 values to Ter and Dob at most, but not all, time points. Two-way analysis of variance (ANOVA) revealed that AUCs, maximum responses, and EC50 values significantly depended on both treatment (endothelium intact/endothelium denuded) and time of sacrifice. Results of the present study clearly show that in vitro sensitivity of rat thoracic aorta to beta-adrenergic agonists displays temporal variations depending on the time of animal sacrifice, and the presence of endothelium modifies the rhythmicity in beta-adrenergic activity. These variations may be due to the circadian rhythmicity in the adenylyl cyclase-cAMP-phosphodiesterase system that mediates the responses to beta-adrenergic agonists.

The effects of captopril and naloxone on restraint-cold-stress- and ethanol-induced gastric lesions in rats.

1. This study was undertaken to investigate the effect of captopril (1 microgram/kg or 1 mg/kg, i.p.) on the actions of naloxone (5 mg/kg, i.p. in gastric ulceration induced by ethanol and restraint-cold-stress. 2. Neither naloxone (5 mg/kg, i.p.) nor captopril (1 mg/kg, i.p.) alone induced any change in the indices of the ulcer in either group. 3. Captopril at a lower dose (1 microgram/kg, i.p.), when combined with naloxone (5 mg/kg, i.p.), significantly reduced cumulative ulcer length only in the ethanol-treated group (from 54.9 +/- 7.2 mm to 22.5 +/- 6.2 mm). 4. However, a high dose of captopril (1 mg/kg) plus naloxone pretreatment caused a significant reduction in both ethanol (from 54.9 +/- 7.2 mm to 24.9 +/- 6.5 mm) and restraint-cold-stress (from 19.0 +/- 3.0 mm to 5.3 +/- 1.0 mm)-induced ulcer formation. 5. Acetylsalycilic acid, when used together with captopril, increased the ulcer formation induced by stress. 6. Naloxone, by increasing the release of prostaglandins, has been shown to prevent ulcer formation induced by several noxious stimuli. 7. Therefore, the effect of the combination might be due to the synergistic interaction of both drugs on prostaglandin synthesis.

Twenty-four-hour variations in the effect of nitrodilators in rat aorta: lack of influence of the endothelium.

Time-dependent variations of the vasodilator effects of sodium nitroprusside and glyceryl trinitrate on isolated smooth muscle have been studied on rings of rat thoracic aorta, both endothelium-intact and endothelium-denuded. For most of the concentrations of sodium nitroprusside used the induced relaxations were significantly dependent on the time the tissues were obtained. However, significant temporal differences were obtained for glyceryl trinitrate-induced relaxations at lower concentrations only for both endothelium-intact and endothelium-denuded preparations. EC50 values of sodium nitroprusside and glyceryl trinitrate (i.e. the concentrations inducing half the maximum response) were also significantly different and they had quite similar rhythmic features both in endothelium-intact and in endothelium-denuded preparations. These results clearly show that the in-vitro sensitivity of rat thoracic aorta to nitrodilator agents varies over a 24-h period and thus depends on when the animals were killed; the presence of endothelium does not change the rhythm of nitrodilator activity. These variations might be a result of circadian rhythm in the guanylate cyclase-cGMP system which mediates responses to nitrodilator agents.

Tween 80 and endothelium: functional reduction due to tissue damage.

The effects of Tween 80, a surface active agent which is frequently used for dispersion of water-insoluble substances, on endothelial function in rabbit aorta, were investigated in a cascade superfusion bioassay system by using a deendothelized precontracted rat aorta ring as a bioassay tissue. Prior incubation of rabbit thoracic aorta segments with higher concentrations of Tween 80, caused total inhibition of acetylcholine-induced endothelium derived relaxing factor (EDRF) release, while moderate concentrations had no significant effect. Perfusion of the donor aortae segments with 10 (-1) - 10 (-3) ml/1 Tween 80 also inhibited the EDRF release from donor aorta dose-dependently. Histopathological examination of the vasculary wall and endothelial structures revealed a significant desquamation of vasculary endothelium with the highest concentration of Tween 80 used in this study. These data suggest that the mechanism underlying the reduction in the release of EDRF from donor aorta segments may be the destruction by Tween 80 of endothelial lining.

The effects of endothelin peptides in the rabbit isolated perfused kidney.

1. Endothelin-1 (21-amino acids) and pre-pro endothelin-1 (39-amino acids) produced a concentration-dependent increase in perfusion pressure when infused through the renal artery of rabbit isolated perfused kidney. Addition of phosphoramidon to the medium caused a potentiation in the vasoconstrictor response to endothelin-1 and greatly, but not completely, inhibited vasoconstriction induced by pre-pro-endothelin-1. 2. Addition of indomethacin to the medium did not alter the vasoconstrictor effects of the peptides. 3. Methylene blue in the medium caused a highly significant potentiation in the vasoconstrictor response to endothelin-1. 4. A short-term infusion of endothelin-1 through the renal artery elicited a decrease in urine flow which returned to control levels after perfusing the kidney with Krebs buffer, but prolonged infusion of the peptide produced an irreversible increase in urine flow. 5. Phosphoramidon, methylene blue and indomethacin failed to alter the effect of endothelin-1 on urine flow. 6. From these results it was concluded that phosphoramidon-sensitive endothelin-converting enzyme, probably localized in microvasculature of the kidney, can convert pre-pro-endothelin-1 to endothelin-1 which is responsible for the vasoconstrictor effect of pre-pro-endothelin-1 in addition to its possible direct vasoconstrictor effect on kidney vasculature. Moreover, the endothelin-1 degradating enzyme in kidney should be a phosphoramidon-sensitive metalloproteinase(s). The results also indicated the release of EDRF but not prostanoids by endothelin-peptides in the rabbit isolated perfused kidney.