Stage I nonseminomatous germ-cell testicular cancer--management options and risk-benefit considerations

The results obtained with primary retroperitoneal lymph-node dissection (RPLND) in 464 patients with clinical stage A nonseminomatous germ-cell (NSGC) testicular cancer over a period of 25 years (1965-1989) were reviewed. Results were analyzed in clinical terms and subdivided into early (1965-1978) and contemporary (1979-1989) findings so as to be comparable with series using radiotherapy or surveillance. Between 1965 and 1978 (86 clinical stage A patients), the overall relapse rate of 15% (n = 13) was similar to that obtained in radiotherapy series but the survival (98.8% after RPLND) was superior to that achieved with irradiation (87%). From 1979 to 1989, 378 clinical stage A cases had primary RPLND, of whom 29% (n = 111) had cancerous nodes. The relapse rate for pathological stage A patients (n = 267) was 11% and two patients died. The rate of relapse for pathological stage B patients who did not receive adjuvant chemotherapy was 32%. No relapse was seen among 46 pathological stage B patients given postoperative adjuvant chemotherapy. The mortality of 0.7% observed among 378 clinical stage A RPLND cases was lower than the 2% value reported in surveillance series. Although not statistically significant, these consistent results reported for two eras (pre- and postplatinum) spanning a period of 25 years suggest a sound basis for the surgical approach. The anatomic and medical principles in oncology, which have supported this approach, remain cogent today. They are discussed herein. Now that nerve-sparing techniques have been developed, the one long-term morbidity of RPLND (i.e., anejaculation) can be avoided.(ABSTRACT TRUNCATED AT 250 WORDS)

Vascular considerations in postchemotherapy. Retroperitoneal lymph-node dissection: Part II

A total of 710 patients underwent postchemotherapy retroperitoneal lymph-node dissection (RPLND) from 1965 to 1992. Ten patients, all with bulky disease, required aortic replacement either postoperatively (n = 3) or during RPLND (n = 7). The principal risk factor for aortic rupture after RPLND was an extended subadventitial aortic dissection made necessary by tumor fixation. Also, duodenal enterotomy or extensive violation of the bowel serosa was a further risk for aortoenteric fistula. Prospective aortic grafting may be indicated in the presence of these risk factors. In our four elective cases, there was no further vascular or bowel complication. Omental interposition further protects against fistula formation. Although rarely indicated except under the most extenuating circumstances, the exposure requirements of RPLND permit aortic grafting as a relatively straightforward procedure that is feasible and well tolerated in this small subset of patients.

Electrical stimulation of the posterior and ventromedial hypothalamic nuclei causes specific activation of shivering and nonshivering thermogenesis

Experiments were designed to determine in the same animal whether electrical stimulation of the posterior hypothalamus and ventromedial hypothalamic nucleus could specifically evoke shivering and nonshivering (brown adipose tissue) thermogenesis, respectively, in anesthetized, normothermic rats. Urethane-anesthetized, male Long-Evans rats, kept at 37 degrees C, had colonic (Tc), gastrocnemius muscle (Tm), intrascapular brown adipose tissue (TIBAT), and tail (Tt) temperatures measured via thermistor probes, and electromyogram activity (differential multiunit activity from bipolar recording electrodes within gastrocnemius muscle) recorded, before and after unilateral electrical stimulation (monophasic 0.5-ms pulses of 200 microA at 50 Hz for 30 s) of the posterior hypothalamus and ventromedial hypothalamic nucleus (via stereotaxically implanted concentric stimulating electrodes). Each rat showed shivering (increased electromyogram activity) following posterior hypothalamic stimulation, which caused an immediate rise in Tm values with no change in TIBAT or Tt values. Electrical stimulation of the ventromedial hypothalamic nucleus of the same animals elicited no shivering activity, but significant increases in TIBAT values occurred with no change in Tm or Tt values. Results confirm that stimulation of the posterior and ventromedial hypothalamic nuclei in rodents specifically activates shivering and nonshivering (brown adipose tissue) effector mechanisms, respectively, to raise core temperature.

Primary retroperitoneal lymph node dissection in clinical stage A non-seminomatous germ cell testis cancer. Review of the Indiana University experience 1965-1989

The results of primary retroperitoneal lymph node dissection (RPLND) in 464 patients with clinical stage A non-seminomatous germ cell (NSGC) testis cancer treated over 25 years (1965-1989) were reviewed. The results were analysed in clinical terms and subdivided into early (1965-1978) and contemporary (1979-1989) groups in order to be comparable with series using radiotherapy or surveillance. Between 1965 and 1978 (86 clinical stage A patients) the overall relapse rate of 15% (n = 13) was similar to that of radiotherapy series but survival (97.7% after RPLND) was superior to that achieved with irradiation (87%). From 1979 to 1989, 378 clinical stage A patients had primary RPLND and 30% of them (n = 112) had cancerous nodes. The relapse rate for pathological stage A (n = 266) was 12% and 2 patients died. The relapse rate in pathological stage B patients without adjuvant chemotherapy was 34%. No relapse was seen among 48 pathological stage B patients who received post-operative adjuvant chemotherapy. The death rate was 0.8% among 378 clinical stage A RPLND patients. While not statistically significantly different from death rates reported in current surveillance series, these consistent results spanning 2 eras (before and after cisplatin) over 25 years suggest a sound basis for the surgical approach. The anatomical and medical principles in oncology, which have supported this approach, still remain cogent today. Now that nerve-sparing techniques have been developed, the only long-term morbidity of RPLND (anejaculation) has been avoided. It would seem appropriate to include nerve-sparing RPLND techniques in the management of clinical stage A disease.

Stimulation of the hypothalamic paraventricular nucleus causes systemic venoconstriction

Venous capacitance plays an important role in cardiovascular homeostasis. The anatomical loci within the central nervous system involved in modulating venous function remain to be elucidated. Stimulation of the hypothalamic paraventricular nucleus is known to increase sympathoadrenal outflow and arterial blood pressure. The present study was undertaken to determine whether electrical stimulation of the paraventricular nucleus can also affect the venous circulation. Mean circulatory filling pressure (MCFP) was used as an index of venous tone. Male Long Evans rats were initially anesthetized with pentobarbital (i.p.; 60 mg/kg) and subsequently maintained with urethane (i.v.; 600 mg/kg). Blood pressure and systemic venous pressure were monitored via catheters in the femoral artery and vein and heart rate was derived from the pulsatile blood pressure signal. A latex tipped balloon was placed in the right atrium via the right jugular vein. Mean circulatory filling pressure was calculated from the arterial and venous plateau pressures recorded during five second balloon inflations. Arterial pressure, systemic venous pressure, heart rate and mean circulatory filling pressure were monitored before and during unilateral monopolar electrical stimulation (0.5 ms pulses at 50 Hz for a train duration of 10 s with constant current intensities of 100, 150, 200, and 300 microA) of the paraventricular nucleus. Increased graded stimulation of the paraventricular nucleus increased blood pressure by 6 +/- 2, 8 +/- 1, 13 +/- 2 and 26 +/- 5 mm Hg while heart rate changed by -22 +/- 6, -18 +/- 6 and -15 +/- 9 bpm and +10 +/- 10 bpm, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Retroperitoneal lymphadenectomy for clinical stage A testis cancer (1965 to 1989): modifications of technique and impact on ejaculation

Results with primary retroperitoneal lymphadenectomy in 464 patients with clinical stage A nonseminomatous germ cell testis cancer (1965 to 1989) were reviewed. The false-negative staging error by clinical methods remains at 30%. The relapse rate in pathological stage A cancer patients was 11% (37 of 323), with 2 deaths. For pathological stage B disease 64% of the patients were cured by retroperitoneal lymphadenectomy alone. With modern adjuvant chemotherapy no stage B tumor relapsed since 1979 and the survival rate was 100%. For all 25 years (464 patients) the relapse rate was 14% and the survival rate was 98.9% (3 cancer and 2 noncancer deaths). Because these results are based on preoperative clinical staging, they are directly comparable with series using radiotherapy or surveillance.

Resection of the inferior vena cava or intraluminal vena caval tumor thrombectomy during retroperitoneal lymph node dissection for metastatic germ cell cancer: indications and results

A total of 42 patients underwent inferior vena caval resection (40) or intraluminal tumor thrombectomy (2) during retroperitoneal lymph node dissection for bulky abdominal metastatic nonseminomatous germ cell cancer (7% of all post-chemotherapy retroperitoneal lymph node dissection cases). The 3 indications for vena caval resection included tumor clearance (38%), vena caval scar occlusion (14%) and vena caval tumor thrombus (48%). En bloc vena caval resection to achieve tumor clearance was justified by subsequent nodal pathology (cancer in 63% of the specimens and teratoma in 31%). Vena caval resection in the presence of scar occlusion was de facto required by virtue of its incorporation in the specimen. Vena caval resection or thrombectomy is indicated for intraluminal tumor thrombus because thrombus pathology (cancer 35%, teratoma 45% and fibrosis 20%) reflected nodal pathology in 71% of the patients with cancer, 78% with teratoma and 100% with fibrosis. The complications of vena caval resection were generally transitory. The 71% survival rate justifies this intensive surgical approach because these patients had exhausted all chemotherapy options.

A national programme for testis cancer, the Irish Testis Tumor Registry (ITTR)

The fundamental aims of the ITTR are to perform research into testis cancer and maximize nationwide disease control. Authors compare regional trends: Ireland, England and Wales. In Ireland, between 1961 and 1984 in the 25 to 34 years age group, the mortality rate increased 123%. In contrast, in England and Wales, the number of deaths has decreased by 17%. The highest mortality rates of all, occurred in those Irish aged over 75 years old. The Irish incidence of testis cancer is 2.4 per 100,000 males per year. Seven countries have lower levels than Ireland, while ten countries have higher levels. Incidence was highest in young adults (5.8 per 100,000) with a moderate level seen in the elderly (1.8 per 100,000). Cases of testis cancer, in Ireland, were grouped as seminomas (45%, n = 101) or non seminomas (55%, n = 131). In seminomas, overall three year actuarial survival was 80%, stage I = 94%, stage II = 72% and stages III and IV = 23%. A variety of treatments were utilized and the results are presented. In non-seminomas, overall three year actuarial survival was 65%, with stage I = 95%, stage II = 54% and stages III and IV = 24%; a variety of treatments were used. A further study was designed ot establish whether personnel and the manner of management can influence the outcome in testis cancer. Survival in patients not receiving full dose cytotoxics was significantly lower than those receiving standard doses. Survival was reduced from 72% to 64% when marker assays were omitted and infrequent monitoring with CT scan was associated with reduced survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of prior orchiopexy on stage and prognosis of testicular cancer

Thirty-four cryptorchid testis cancer cases were studied, of whom 9 patients had prior orchiopexy at the time of cancer diagnosis. Disease stage in this group was: stage I = 4, stage II = 1 and stages III and IV = 4 cases. Seventy-eight percent of these cases (n = 7) had non-seminomas; 4 of these patients died. In the uncorrected cryptorchidism group (n = 25), disease stage was: stage I = 12, stage II = 9 and stages III and IV = 4 cases. Of these cases, 64% (n = 16) had seminomas and 6 patients died. Orchiopexy marginally reduced the symptomatic interval for subsequent cancer and probably decreased the risk of seminoma development. Orchiopexy did not lead to a more favourable disease presentation or prognosis because of the adverse bias of advanced-stage non-seminomas in this group.

Brown adipose tissue thermogenesis is activated by electrical and chemical (L-glutamate) stimulation of the ventromedial hypothalamic nucleus in cold-acclimated rats

Experiments were conducted to determine if both electrical and chemical stimulation of the ventromedial hypothalamic nucleus (VMH) could activate brown adipose tissue (BAT) thermogenesis. Age-matched, room-acclimated (21 degrees C) and cold-acclimated (4 degrees C for 3 weeks prior to testing) male Sprague-Dawley rats were given unilateral electrical or chemical stimulation to the VMH by way of a 'chemotrode apparatus'. The devised 'chemotrode' allowed both electrical stimulation (insulated piano wire stimulating electrode) and chemical stimulation (23 gauge stainless steel intracranial cannula of equal length) to be performed at the same VMH site using a common 19 gauge stainless steel outer guide tube. The first unilateral VMH electrical stimulation (0.5 ms pulse, 50 Hz and 120 microA for 30 s) caused no significant rise in interscapular brown adipose tissue temperature (TIBAT) colonic (Tc) or tail surface temperatures (Tt), compared to respective prestimulation control values in rats acclimated to 21 degrees C. In the 4 degrees C-acclimated group the first VMH electrical stimulation caused a significant rise in IBAT temperature. L-Glutamate administration to the same VMH site (60 nmol in 600 nl volume) also caused a significant increase in IBAT temperature in the 4 degrees C but not the 21 degrees C-acclimated rats. The rise in IBAT temperature following the L-glutamate injection to the 4 degrees C-acclimated group was similar to that found following the first electrical stimulation to this group. Interestingly, a second unilateral electrical stimulation of the VMH to 4 degrees C-acclimated rats could not evoke a similar increase in IBAT temperature suggesting that overall L-glutamate was acting in vivo as an excitotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracorporeal shockwave lithotripsy monotherapy for paediatric urinary tract calculi

The role of extracorporeal shockwave lithotripsy (ESWL) in the management of paediatric urinary tract calculi was evaluated. The study group included 22 children (13 male, 9 female) with an age range of 2 to 13 years. The renal calculi, including staghorn and ureteric calculi, varied in size from 0.3 to 5 cm. Overall stone clearance at 3 months was 79% with a low incidence of complications (2 children required nephrostomy drainage for sepsis). ESWL is a non-invasive method of managing even complex stones in children of all ages, irrespective of size or position.

Hemodynamic responses of conscious rats following intrathecal injections of prodynorphin-derived opioids: independence of action of intrathecal arginine vasopressin

Experiments were conducted (i) to determine the hemodynamic (blood pressure and heart rate) responses of conscious rats following intrathecal (IT) administration of endogenous prodynorphin-derived opioids into the lower thoracic space, (ii) to identify the receptors involved in mediating their cardiovascular responses, and (iii) to reveal any possible hemodynamic interactions with the neuropeptide arginine vasopressin. Male Sprague-Dawley rats were surgically prepared with femoral arterial and venous catheters as well as a spinal catheter (into lower thoracic region, T9-T12). After recovery, hemodynamic responses were observed in conscious rats for 5-10 min after IT injections of artificial cerebrospinal fluid (CSF) solution, prodynorphin-derived opioids (dynorphin A, dynorphin B, dynorphin A (1-13), dynorphin A (1-10), alpha- and beta-neoendorphin, leucine enkephalin (LE), methionine enkephalin (ME), arginine vasopressin (AVP), or norepinephrine (NE)). IT injections of AVP (10 or 20 pmol), dynorphin A (1-13), or dynorphin A (10-20 nmol) caused pressor effects associated with a prolonged and significant bradycardia. Equimolar (20 nmol) concentrations of LE, ME, alpha- and beta-neoendorphin, and dynorphin A (1-10) caused no significant blood pressure or heart rate changes. Combined IT injections of dynorphin A (1-13) and AVP caused apparent additive pressor effects when compared with the same dose of either peptide given alone. IT infusion of the specific AVP-V1 antagonist d(CH2)5Tyr(Me)AVP before subsequent IT AVP, dynorphin A (1-13), or NE administration inhibited only the subsequent pressor responses to AVP. The kappa-opioid antagonist (Mr2266) infused IT blocked the pressor actions of subsequent dynorphin A administration and not AVP or NE.(ABSTRACT TRUNCATED AT 250 WORDS)

Intrathecal dynorphin A administration causes pressor responses in rats associated with an increased resistance to spinal cord blood flow

Hemodynamic responses (blood pressure, as well as cardiac output (CO), peripheral and CNS blood flow changes measured via radioactive microspheres) were analyzed in anesthetized rats 2 min following intrathecal (IT) administration (10 microliters) of either 5-ion control solution or 20 nmol of dynorphin A(1-13) into the lower thoracic space (T10-T12). Mean arterial pressure (MAP) significantly increased within 2 min following IT dynorphin A(1-13) due to rise in total peripheral resistance, whereas CO significantly declined. Two minutes post-IT-dynorphin A(1-13) administration spinal cord blood flow also significantly decreased for 2 cm anterior and 1 cm posterior from the tip of the spinal catheter, which reflected a significant elevation in tissue flow resistance of spinal cord vessels in spite of the reduction of CO. As well, tissue blood flow resistance was also increased at this time in the kidneys and adrenal glands. The results indicate that within 2 min after intrathecal dynorphin A(1-13) administration an acute increase in blood flow resistance of spinal cord vessels around the tip of the spinal catheter occurs, at a time when the animal is also hypertensive. It is suggested that the associated pressor response may, in part, be caused by dynorphin A evoking localized ischemia.

Intravenous morphine infusion (IMF) to drug-naive, conscious rats evokes bradycardic, hypotensive effects, but pressor actions are elicited after IMF to rats previously given morphine

Hemodynamic (blood pressure and heart rate) responses of conscious drug-naive rats were studied following intravenous (i.v.) infusion of sterile saline, morphine sulphate, and then naloxone hydrochloride, as well as of other groups previously injected with morphine sulphate. Those groups chronically given morphine sulphate received twice daily injections of morphine sulphate (5 mg/kg, s.c. per injection) for 3 or 6 days before testing with the i.v. infusion of morphine sulphate. Drugs were infused (135 microL/min) through an indwelling femoral venous catheter via a Harvard infusion pump, and blood pressure was recorded from the abdominal aorta via a femoral arterial catheter. Other pretreatment studies were done to determine the receptor mechanisms mediating the blood pressure responses of drug-naive and chronic morphine-treated rats, whereby equimolar doses (0.32 mumol) of specific receptor antagonists were given as a bolus i.v. injection 5 min after saline but before subsequent infusion with morphine sulphate. Intravenous infusion of morphine sulphate (7.5 mg/kg total over 15 min) to drug-native rats caused a transient but precipitous fall in mean arterial pressure and mean heart rate with an associated rise in mean pulse pressure; these effects were blocked in other groups pretreated with atropine. Interestingly, however, rats chronically injected with morphine sulphate for 3 days previously evoked a transient pressor response when subsequently infused i.v. with morphine sulphate, actions that were blocked in other groups when pretreated i.v. with 0.32 mumol of phentolamine, yohimbine, prazosin, or guanethidine. A greater and persistent pressor response occurred following morphine infusion to groups of rats previously injected over 6 days with morphine sulphate, which was associated with tachycardia during the later stages of the 15-min morphine sulphate infusion period. The prolonged pressor and tachycardic responses of this 6-day chronically injected group were completely blocked in another group pretreated i.v. with both phentolamine and propranolol (0.32 mumol). The results suggest that morphine sulphate infusion to conscious, drug-naive rats evokes classical hypotensive effects due to decreases in mean heart rate caused by activation of parasympathetic vagal activity. With 3 or 6 days of chronic morphine sulphate administration beforehand, subsequent i.v. infusion of morphine sulphate evoked pressor actions felt to be caused by a progressive activation of the sympathetic nervous system.(ABSTRACT TRUNCATED AT 400 WORDS)

Opiate and alpha receptor antagonists block the pressor responses of conscious rats given intravenous dynorphin

Conscious, unrestrained rats were used to determine the hemodynamic (blood pressure and heart rate) responses following intravenous (IV) injection of dynorphin A(1-13) and the possible receptor mechanisms mediating those changes. Male Sprague-Dawley rats (300 g) were given IV bolus injections (via femoral venous catheter) of 6.0 to 600 nmoles/kg of dynorphin A(1-13), 8.0 nmoles/kg of norepinephrine HCl (NE), 14.3 pmoles/kg of angiotensin II or a vehicle control solution. Blood pressure (BP) and heart rate (HR) were monitored via femoral arterial catheter (into abdominal aorta) over 90 sec postpeptide or -amine administration before and 10 min after IV injection of 4.2 mumoles/kg of naloxone HCl (opiate antagonist), yohimbine HCl (alpha 2 receptor antagonist) or prazosin HCl (alpha 1 receptor antagonist). Dynorphin A(1-13) caused a transient but dose-related rise in mean arterial pressure (MAP) whereas mean pulse pressures (MPP) and mean heart rates (MHR) concomitantly fell, from preinjection control values in a dose-dependent fashion. Pretreatment with naloxone blocked the pressor response of only a subsequent injection with 20 nmoles/kg but not 60 nmoles/kg of dynorphin A or NE (8.0 nmoles/kg). Pretreatment with yohimbine suppressed the marked pressor responses of subsequent NE or Dyn A (60 nmoles/kg) administration whereas prazosin antagonized the rise in MAP of only the lower doses of dynorphin as well as NE. The suppression of the pressor responses of dynorphin by opiate or alpha receptor antagonists were not caused by tachyphylaxis for repeated injections of 6.0 or 60 nmoles/kg of dynorphin caused the same rise in MAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Physician-dependent prognostic variables in the management of testicular cancer

A study of 246 cases of germ cell testicular cancer in Ireland between 1980 and 1985 confirmed that the personnel and the manner of management can significantly influence the outcome. Inadequate staging by omitting marker assays or CT scan reduced prognosis. Failure to use standard chemotherapy (PVB, BEP, POMBACE, VAB) or a reduced dosage diminished survival. Regular investigations are necessary during treatment, including marker assays, chest X-ray and CT scan. Frequent monitoring is important in later follow-up. Management by a urologist improved survival, especially if he was involved from the outset. The results also favoured the concept of combined management by a urologist and an oncologist.

Non-seminomatous germ cell testis cancer in Ireland (1980-1985). Management, results and prognostic variables with relevance to national management protocols

All non-seminomatous germ cell testis cancer in Ireland (1980-1985) was analysed (n = 131) and 3-year survival was: stage I = 95% (n = 58), stage II = 54% (n = 36), stages III and IV = 24% (n = 34). Countrywide results were not as favourable as those achieved in specialist units and this supports the development of a national strategy to maximise disease control. No management protocols existed during this study and the variety of approaches helped to identify the most suitable types of treatment in this broad context.

An evaluation of predisposing factors for testis cancer in Ireland

All testis cancer in Ireland (1980-1985) was analysed (n = 240). Incidence was highest in young adults (5.8/10(5)/year in those aged 25-34 years) with a moderate level in the elderly (1.8/10(5)/year in those over 75 years). Associations elsewhere with maldescent and social class were confirmed but cryptorchidism (12%) was more common than expected. Significant infertility was not identified. Associations with urban domicile (77%, p = 0.001), mental handicap (2.8%, p less than 0.05), recent vasectomy (1.2%, p = 0.009) and certain occupations were observed.

Pressor, tachycardic and feeding responses in conscious rats following i.c.v. administration of dynorphin. Central blockade by opiate and alpha 1-receptor antagonists

Experiments were designed to determine the hemodynamic responses of conscious, unrestrained rats given intracerebroventricular (i.c.v.) injections of dynorphin A-(1-13) and the possible central receptor mechanisms mediating those changes. Male Sprague-Dawley rats (300 gb. wt.) received i.c.v. injections (by gravity flow in a total volume of 3 or 5 microliter) of control solutions of sterile saline (SS) or dimethylsulfoxide (DMSO) or 1.5, 3.0 or 6.1 nmol of dynorphin A-(1-13). Blood pressure and heart rate changes were monitored over 2 h after administration; as well, feeding activity was visually assessed and scored over this period. Other groups of conscious rats were pretreated i.c.v. with equimolar doses (3.0-24.4 nmol) of specific receptor antagonists (naloxone HCl, phentolamine HCl, propranolol HCl, yohimbine HCl or prazosin HCl) 10 min before subsequent i.c.v. administration of SS or DMSO/SS or 6.1 nmol of dynorphin A-(1-13). I.c.v. injection of dynorphin A-(1-13) caused a dose-related pressor response, associated temporally with tachycardia. As well, dynorphin evoked feeding activity and some grooming, which occurred when the rats were hypertensive and tachycardic and decreased as heart rate and blood pressure returned to control levels. I.c.v. pretreatment studies indicated that naloxone HCl (12.2 nmol), phentolamine HCl (12.2 nmol) and prazosin HCl (6.1 nmol) blocked the pressor response, tachycardia as well as feeding activity of rats subsequently given dynorphin. The results suggest the pressor and tachycardic effects of conscious rats following i.c.v. dynorphin administration may, in part, be due to behavioral activation (feeding). As well, these data indicate that both opioid as well as alpha 1-adrenergic receptors within the CNS are involved in mediating the pressor, tachycardic and feeding responses of conscious rats given i.c.v. injections of dynorphin A.

The effects of endogenous opioids on tension development of isolated, electrically stimulated rat atria

The possible inotropic effects of all three classes of endogenous opioids were tested alone or in combination with noradrenaline, adrenaline, or carbachol on electrically stimulated atria isolated from male Sprague-Dawley rats. Noradrenaline (6.0 and 12 microM) and adrenaline (4.0 and 8.0 microM) injections caused marked but transient (5 min) dose-related increases in atrial tension compared with preinjection control values, whereas carbachol (0.14 and 1.4 microM) caused a more potent and prolonged (over 15 min) dose-related decrease in atrial tension development. Adrenal enkephalins (0.3-4.0 microM) of methionine enkephalin, leucine enkephalin, Met-enkephalin-Arg6-Phe7, and Met-enkephalin-Arg6-Gly7-Leu8, beta-endorphin (0.2-2.0 microM), or dynorphin A(1-13) (0.2-2.0 microM) did not change atrial tension for a 15-min postadministration test period. In addition, these opioids did not affect the positive inotropic effects of noradrenaline (12 microM) or adrenaline (8.0 microM) or the negative inotropic actions of carbachol (1.4 microM) when the same doses of noradrenaline, adrenaline, or carbachol were given alone. These data indicate that endogenous opioids given in micromolar concentrations tested did not affect atrial tension development of electrically stimulated rat atria. Comparing these data with those of past literature, it is suggested that circulating endogenous opioids probably do not have any direct effects on the rat myocardium to affect myocardial contractility.