Kinetic analysis of LY320236: competitive inhibitor of type I and non-competitive inhibitor of type II human steroid 5alpha-reductase.

Type I and type II steroid 5alpha-reductases (5alpha-R) catalyze the conversion of testosterone (T) to dihydrotestosterone (DHT). LY320236 is a benzoquinolinone (BQ) that inhibits 5alpha-R activity in human scalp skin (Ki(typeI)=28.7+/-1.87 nM) and prostatic homogenates (Ki(typeII)=10.6+/-4.5 nM). Lineweaver-Burk, Dixon, and non-linear analysis methods were used to evaluate the kinetics of 5alpha-R inhibition by LY320236. Non-linear modeling of experimental data evaluated V(max) in the presence or absence of LY320236. Experimental data modeled to the following equation 1v=+ fixing the In0c value equal to 1.0 or 0 are consistent with non-competitive or competitive inhibition, respectively. LY320236 is a competitive inhibitor of type I 5alpha-R (In0c=0, Ki=3.39+/-0.38, RMSE = 1.300) and a non-competitive inhibitor of type II 5alpha-R (In0c=1, Ki=29. 7+/-3.4, RMSE = 0.0592). These data are in agreement with linear transformation of the data using Lineweaver-Burk and Dixon analyses. These enzyme kinetic data support the contention that the BQ LY320236 is a potent dual inhibitor with differing modes of activity against the two known human 5alpha-reductase isozymes. LY320236 represents a class of non-steroidal 5alpha-R inhibitors with potential therapeutic utility in treating a variety of androgen dependent disorders.

In vivo effects of a novel thromboxane A2/prostaglandin H2 (TXA2/PGH2) partial agonist, (+)5(Z)-7-[3-endo-phenylsulfonylamino[2.2.1]- bicyclohept-2-exo-yl]-heptenoic acid [(+)-S-145], on vascular, platelet and cardiac function.

A novel thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptor ligand, (+)5(Z)-7-[3-endo-phenylsulfonylamino[2.2.1]-bicyclohept-2-e xo- yl]-heptenoic acid [(+)-S-145], was evaluated in guinea pigs to assess the in vivo pharmacodynamic profile of this compound at vascular, cardiac and platelet TXA2/PGH2 receptors. Comparison was made to the TXA2/PGH2 receptor antagonist SQ29548. Upon i.v. injection, (+)-S-145, but not SQ29548, elicited transient (approximately 1 min) increases in mean arterial blood pressure (ED50 +/- 95% confidence limit = 6.1 + 4.0, -2.2 micrograms/kg). The potency of i.v. (+)-S-145 (ID50 = 6.3 + 2.3, -2.3 micrograms/kg) against the pressor response to subsequent i.v. TXA2/PGH2 mimetic, U44069, was 9.5-fold greater than that of SQ29548 (ID50 = 59.1 + 52.9, - 52.9 micrograms/kg). Intravenous (+)-S-145 inhibited U44069-induced decreases in circulating platelet count (ID50 = 4.2 + 4.1, - 2.0 micrograms/kg). In thoracotomized guinea pigs, i.v. (+)-S-145 (31.6 micrograms/kg) and increasing i.v. doses of U44069 increased mean arterial blood pressure, total peripheral resistance, left ventricular end-diastolic pressure and left ventricular peak positive dP/dt (LV + dP/dt) and depressed cardiac output (P < .05). Pretreatment with i.v. (+)-S-145 (31.6 micrograms/kg) abolished these U44069-induced effects. In thoracotomized guinea pigs in which left ventricular end-diastolic pressure and HR were held constant, U44069 again increased LV + dP/dt (P < .05), but (+)-S-145 decreased LV + dP/dt (P < .05), which indicates the lack of an (+)-S-145 direct inotropic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative QSAR studies of two series of 1,4-dihydropyridines as slow calcium channel blockers.

Quantitative structure activity analysis was applied to two series of dihydropyridine (DHP) calcium channel blocking agents. One series of compounds was composed of DHPs substituted in the 4-position with an ortho or meta nitro substituted phenyl ring. The second group consisted of DHPs substituted at the 4-position with a novel thieno [3,2-c] pyridine ring. Both series consisted of compounds with unsymmetrical ester substitutions on the dihydropyridine ring. The antihypertensive activity of the compounds were determined in a spontaneously hypertensive rat model. Regression analysis indicated the antihypertensive activity of an i.v. dose correlated with the calculated octanol/water coefficent (clogP). Regression analysis did not find correlation with the in vitro potency and the clogP values.

Effect of activation of ATP-dependent potassium channels with (-)-pinacidil and (-)-3-pyridyl pinacidil on infarct size in a canine model of ischemia-reperfusion injury.

We tested the hypothesis that opening myocardial ATP-dependent K+ (ATP-K) channels by administration of (-)-pinacidil or (-)-3-pyridyl pinacidil intracoronarily (i.c.) either during ischemia or as pretreatment could decrease infarct size in a canine model of ischemia-reperfusion injury in anesthetized male hounds subjected to 90-min left circumflex coronary artery (LCX) occlusion followed by 5-h reperfusion. Drugs were administered by one of two protocols. In the postocclusion treatment protocol (protocol post), either vehicle or (-)-3-pyridyl pinacidil [0.25 micrograms/kg/min (low dose) or 1 micrograms/kg/min (high dose)] was infused i.c. distal to the site of coronary artery occlusion, through LCX beginning 10 min after LCX occlusion and continuing until 10 min after the beginning of reperfusion. In the preocclusion treatment protocol (protocol pre), vehicle, low dose (-)-3-pyridyl pinacidil, or (-)-pinacidil (1 micrograms/kg/min) was infused i.c. distal to the site of coronary artery occlusion through the LCX beginning 10 min before occlusion and continuing until the end of the experiment. In both protocols, (-)-pinacidil and (-)-3-pyridyl pinacidil failed to demonstrate a decrease in infarct size from that of the vehicle-treated groups. In protocol post, the mean sizes of the infarcts in the vehicle, low-dose, and high-dose (-)-3-pyridyl pinacidil-treated groups were 26.4 +/- 5.0, 35.6 +/- 6.6, and 28.9 +/- 6.1% of the area at risk, respectively. In protocol pre, the mean sizes of the infarcts in the vehicle, (-)-pinacidil, and low dose (-)-3-pyridyl pinacidil-treated groups were 29.4 +/- 1.7, 27.0 +/- 3.9, and 35.6 +/- 4.1% of the area at risk, respectively. Neither subepicardial nor subendocardial blood flow in the ischemic zone, measured by radioactive microspheres, was significantly different among groups in either protocol. In protocol post, however, the endocardial/epicardial blood flow ration in the nonischemic zone was decreased by (-)-3-pyridyl pinacidil. In addition, the ischemic zone (LCX)/nonischemic left anterior descending coronary artery (LAD) zone blood flow ratio in the subepicardial region were decreased by (-)-3-pyridyl pinacidil. These observations suggest that the drug may shift blood flow away from the ischemic zone in general and away from the endocardium in particular. In protocol pre, the LCX/LAD ratio tended to decrease with both drugs, but the difference achieved statistical significance only with (-)-3-pyridyl pinacidil (low dose).(ABSTRACT TRUNCATED AT 400 WORDS)

Muscarinic M1 receptor agonist actions of muscarinic receptor agonists in rabbit vas deferens.

In the electrically field-stimulated rabbit vas deferens, muscarinic receptor agonists increase twitch-height by actions at postjunctional M2 receptors and decrease twitch-height by actions at prejunctional M1 receptors. In the present studies, in contrast to previous reports, muscarinic receptor agonists primarily decreased twitch-height, produced minimal increases in twitch-height, and, produced identical responses in both epididymal and prostatic tissue segments, thus permitting a more detailed investigation of the M1 receptor component of action of muscarinic receptor agonists in the rabbit vas deferens. The nonselective muscarinic receptor agonist carbachol produced biphasic effects on twitch-height in the vas deferens: lower concentrations increased twitch-height to only approximately 25-30% over control, whereas higher concentrations inhibited the twitch. The selective M1 receptor antagonist pirenzepine blocked the inhibitory effects of carbachol, and unmasked carbachol-induced increases in twitch-height. Atropine, 4-DAMP (4-diphenylacetoxy-N-methylpiperidine methiodide) and AF-DX 116 (11-2[[2-[(diethylamino)methyl]-1-piperidinyl]acetyl]-5,11-dihydro- 6H-pyrido[2,3-b][1,4]benzodiazepin-6-one) blocked both the inhibitory and stimulatory effects of carbachol, but atropine and 4-DAMP were more potent in blocking the inhibitory than the stimulatory effects of carbachol, whereas the reverse was true for AF-DX 116. McN-A-343 (4-hydroxy-2-butynyl)trimethylammonium chloride, m-chlorocarbanilate) and 12 other muscarinic receptor agonists from a variety of chemical classes also produced concentration-dependent decreases in twitch-height. The log IC50s of the muscarinic receptor agonists for decreasing twitch-height were highly correlated with their log Kis for inhibiting [3H]pirenzepine (r = 0.96) and [3H]oxotremorine-M (r = 0.85) binding in rat hippocampal membranes. The present results demonstrate that the muscarinic M1 receptor mediating inhibition of twitch-height in the rabbit vas deferens has pharmacologic properties similar to the muscarinic M1 receptor in rat hippocampus.

Porcine pancreatic phospholipase A2-induced contractions of guinea pig lung pleural strips.

The contractile nature of porcine pancreatic phospholipase A2 (PLA2) was characterized on paired pleural strips obtained from guinea pig lung. PLA2 (0.003-10 U/ml) produced concentration-related contractile responses which were sensitive to various drugs. The major component of the PLA2-induced contractions was derived from products of the cyclooxygenase pathway since a cyclooxygenase inhibitor or the combination of a thromboxane synthetase inhibitor and a thromboxane receptor antagonist produced a 54-65% reduction of the contractile responses. 5-Lipoxygenase products contributed to a smaller component of the PLA2-induced responses since 5-lipoxygenase inhibitors or the combination of a leukotriene (LT) B4 receptor antagonist and an LTD4/LTE4 receptor antagonist only suppressed the maximal responses 22-32%. PLA2-induced contractile responses were nearly abolished by altering both sides of the arachidonic acid cascade simultaneously. In contrast, a PAF receptor antagonist, a histamine (H1) receptor antagonist and an acetylcholine receptor antagonist, failed to significantly reduce PLA2-induced responses. These results demonstrate that exogenous administration of porcine pancreatic PLA2 produced concentration-dependent contractions of pleural strips mediated through the generation of eicosanoids.

Potency and efficacy of dopamine agonists in mouse strains differing in dopamine cell and receptor number.

The potency and efficacy of the selective dopamine D2 receptor agonist quinpirole, the mixed D1/D2 agonist apomorphine, and the selective D1 receptor agonist SKF 38393 in producing hypothermia and changes in locomotor activity were evaluated in four strains of mice: CBA/J, C57BL/6J, ICR Swiss and CF1. CBA/J mice previously have been shown to be deficient in dopamine cell and receptor number relative to other strains such as C57BL/6J mice, whereas ICR Swiss and CF1 are commonly used strains of mice. Quinpirole (0.125 to 1.0 mg/kg) was equiefficacious and equipotent in producing hypothermia in all 4 strains. Apomorphine (0.125 to 16 mg/kg) was equiefficacious in producing hypothermia in all 4 strains, but was approximately four-fold less potent in CBA/J mice than in the other strains. SKF 38393 had little effect on body temperature in any of the 4 strains. Basal motor activity was lowest in CBA/J mice, and tended to be highest in ICR Swiss mice. Quinpirole (0.125 to 32 mg/kg) had no effect on motor activity in CBA/J mice, but decreased motor activity in the other 3 strains. Apomorphine (1 to 16 mg/kg) produced modest increases in motor activity in all 4 strains. The magnitude of the changes produced by apomorphine was comparable in all strains when expressed as change from mean control values. SKF 38393 (8 to 64 mg/kg) also increased motor activity in all 4 strains, with comparable increases when expressed as change from mean control values. The present results are consistent with the interpretation that inherited deficiencies in dopamine cell and receptor number in CBA/J mice produce functional decrements in D2, but not D1, dopamine receptor function.

Distinction between metabolic and myogenic mechanisms of coronary hyperemic response to brief diastolic occlusion.

We monitored an index of coronary vascular resistance (mean aortic pressure/mean coronary flow) in 19 heart-blocked conscious dogs paced at 60 beats/min and instrumented with an aortic pressure catheter, left circumflex artery electromagnetic flow probe, and a coronary occluder. Cessation of pacing for a single beat resulted in a long diastole control (LDC) intervention beat of 2-second duration characterized by a progressive rise in diastolic coronary vascular resistance index. A 400-msec coronary artery occlusion early in a long diastole (LD4) dramatically inhibited the rate of rise in resistance index during the first 600 msec (phase 1) after occlusion. Partial recovery of the resistance index rise rate was evident during the remaining 400 msec (phase 2) of the long diastole. In nine dogs, LDC and LD4 intervention beats were instituted during two conditions of myocardial metabolic activity in which the myogenic stimuli associated with coronary occlusion would be similar: 1) paired pacing and 2) normal pacing plus intravenous adenosine and phenylephrine infusions (AP) to maintain mean aortic pressure and coronary flow at paired pacing levels. During paired pacing, the LD4-LDC differences in phase 1 and 2 resistance index rise rates (-69 +/- 18 and -48 +/- 31 mmHg/ml/sec2, respectively) were greater than during normal pacing plus AP (-32 +/- 14 and -1 +/- 32 mm Hg/ml/sec2, phase 1 and 2, respectively) (p less than 0.05). These differences are consistent with operation of a metabolic mechanism in response to occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Chiral recognition of pinacidil and its 3-pyridyl isomer by canine cardiac and smooth muscle: antagonism by sulfonylureas.

Pinacidil, a potassium channel opener (PCO), relaxes vascular smooth muscle by increasing potassium ion membrane conductance, thereby causing membrane hyperpolarization. PCOs also act on cardiac muscle to decrease action potential duration (APD) selectively. To examine the enantiomeric selectivity of pinacidil, the stereoisomers of pinacidil (a 4-pyridylcyanoguanidine) and its 3-pyridyl isomer (LY222675) were synthesized and studied in canine Purkinje fibers and cephalic veins. The (-)-enantiomers of both pinacidil and LY222675 were more potent in relaxing phenylephrine-contracted cephalic veins and decreasing APD than were their corresponding (+)-enantiomers. The EC50 values for (-)-pinacidil and (-)-LY222675 in relaxing cephalic veins were 0.44 and 0.09 microM, respectively. In decreasing APD, the EC50 values were 3.2 microM for (-)-pinacidil and 0.43 microM for (-)-LY222675. The eudismic ratio was greater for the 3-pyridyl isomer than for pinacidil in both cardiac (71 vs. 22) and vascular (53 vs. 17) tissues. (-)-LY222675 and (-)-pinacidil (0.1-30 microM) also increased 86Rb efflux from cephalic veins to a greater extent than did their respective optical antipodes. The antidiabetic sulfonylurea, glyburide (1-30 microM), shifted the vascular concentration-response curve of (-)-pinacidil to the right by a similar extent at each inhibitor concentration. Glipizide also antagonized the response to (-)-pinacidil, but was about 1/10 as potent with a maximal shift occurring at 10 and 30 microM. Glyburide antagonized the vascular relaxant effects of 0.3 microM (-)-LY222675 (EC50, 2.3 microM) and reversed the decrease in APD caused by 3 microM (-)-LY222675 (EC50, 1.9 microM). Nitroprusside did not alter 86Rb efflux, and vascular relaxation induced by sodium nitroprusside was unaffected by sulfonylureas. Thus, the enantiomers of the 3-pyridyl isomer of pinacidil demonstrate enhanced stereospecificity in both canine cardiac and vascular tissues compared to the enantiomers of pinacidil. However, the relative selectivity of pinacidil and its 3-pyridyl isomer for cardiac and vascular smooth muscle remains unaltered. Sulfonylureas antagonize the more potent enantiomers in both tissues, supporting the involvement of an ATP-sensitive potassium channel in the action of PCOs; however, antagonism in canine vascular smooth muscle by sulfonylureas does not resemble classical competitive antagonism.

Effects of oral pergolide mesylate on nociceptive spinal cord reflexes in rats.

The effects of orally administered pergolide mesylate on the flexor reflex were evaluated in chronic spinal rats. The mixed D1/D2 agonist pergolide (0.1 to 3.0 mg/kg) produced a dose-related decrease in the magnitude of the flexor reflex elicited by a tetanic stimulus. The effects of pergolide were blocked by haloperidol, demonstrating that the effects of pergolide were mediated through dopamine receptors. In contrast, the selective D2 agonist bromocriptine (3.0 to 30 mg/kg) had no effect on the flexor reflex. The present results are consistent with the interpretation that pergolide produces an antinociceptive action at the spinal cord level by stimulating both D1 and D2 dopamine receptors.

Interactions between scopolamine and muscarinic cholinergic agonists or cholinesterase inhibitors on spatial alternation performance in rats.

The effects on working memory of the muscarinic cholinergic agonists oxotremorine, arecoline, RS86 and pilocarpine, and the cholinesterase inhibitors physostigmine and tetrahydroaminoacadine were investigated in male F344 rats. Working memory was assessed by behavior maintained under a spatial alternation schedule of food presentation in which the interval between trials was varied from 2 to 32 sec. Under control conditions the percentage of correct responses decreased as the retention interval was varied from 2 to 32 sec. Administered alone the cholinergic agonists oxotremorine (0.01-0.1 mg/kg), arecoline (3-30 mg/kg), RS86 (0.3-3 mg/kg) and pilocarpine (0.3-3.0 mg/kg), and the cholinesterase inhibitors physostigmine (0.01-0.1 mg/kg) and tetrahydroaminoacridine (0.3-3.0 mg/kg) either had no effect on or produced dose-related deficits in working memory and decreases in response rates. The muscarinic antagonist scopolamine (0.1 mg/kg) produced retention interval-dependent decreases in the percentage of correct responding and rates of responding. The cholinergic agonists and tetrahydroaminoacridine failed to reverse the effects of scopolamine. However, physostigmine produced a dose-dependent reversal of the working-memory deficits and response-rate decreasing effects of scopolamine. The present results are consistent with the interpretation that drugs which primarily enhance M2 muscarinic cholinergic transmission are ineffective in enhancing working memory or in reversing scopolamine-induced deficits in working memory.

Leukotriene receptor antagonism and augmentation of beta-receptor-mediated events by LY171883.

LY171883, (1-[2-hydroxy-3-propyl-4-[4(1H-tetrazol-5-yl)butoxy)phenyl]etha none), a leukotriene (LT) D4/E4 receptor antagonist, was assessed in comparison with two well known phosphodiesterase inhibitors, isobutylmethyl-xanthine (IBMX) and theophylline, for its ability to augment beta-receptor-mediated responses. Relaxation of carbachol-contracted guinea-pig trachea by isoprenaline was enhanced by the three agents in a dose-dependent manner. A two-fold enhancement of isoprenaline-induced smooth muscle relaxation was produced by 2.5 microM IBMX, 28 microM LY171883, or 140 microM theophylline. Similar concentrations of IBMX or theophylline did not antagonize LTE4-induced tracheal contractions; LY171883 totally inhibited the response and had significant LTE4 receptor antagonist activity even at 10-fold lower concentrations. Antigen-induced release of histamine and LTC4 from guinea-pig lung was reduced by isoprenaline. Prior treatment with LY171883, IBMX, or theophylline did not enhance this action. Isoprenaline reduced histamine-induced bronchospasm in anaesthetized guinea-pigs. LY171883, 30 mg kg-1, or IBMX, 1 mg kg-1, did not affect the isoprenaline-induced decrease in the histamine response. IBMX, 3 mg kg-1, and theophylline, 30 mg kg-1, augmented the isoprenaline-induced bronchodilation. LTE4-induced bronchoconstriction was not affected by IBMX or theophylline whereas LY171883 antagonized this response at doses as low as 3 mg kg-1. Therefore, in both in-vitro and in-vivo test systems, LY171883 functioned primarily as a leukotriene receptor antagonist with minimal pharmacological activity attributable to its ability to potentiate isoprenaline.

Assessment of working memory in rats using spatial alternation behavior with variable retention intervals: effects of fixed-ratio size and scopolamine.

The effects of fixed-ratio (FR) size, scopolamine, and the interactions between FR size and scopolamine were investigated in male F344 rats on working memory as assessed by spatial alternation behavior maintained under FR schedules of food presentation where the interval between trials was varied among values of 2, 4, 8, 16, and 32 s within each session. The magnitude of the FR size on the correct and incorrect levers was varied systematically from 1 response to 2, 4, 8, or 16 responses in order to determine whether the FR size influenced either the percentage of correct responding, rates of responding, or both. Under the primary baseline condition, that is when the FR size on both the correct and incorrect levers was one response (designated FR1 FR1), the percentage of correct responses decreased with increasing retention interval duration. Increasing the FR size on the correct lever produced FR-dependent increases in the percentage of correct responding as well as in rates of responding. Increasing the FR size on the incorrect lever produced FR-dependent decreases in correct responding, but had little effect on rates of responding. Dose-effect curves for scopolamine were determined on performance maintained under FR values on the correct and incorrect levers, respectively, of FR1 FR1, FR1 FR10, FR10 FR1, and FR10 FR10. In general, scopolamine produced dose-related decreases in the percentage of correct responding, although the magnitude of the effects of scopolamine varied not only with dose, but also with the length of the retention interval and with changes in FR size.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug treatments for metastasis of the Lewis lung carcinoma: lack of correlation between inhibition of lung metastasis and survival.

The abilities of the Eli Lilly compounds LY150310, LY189332, and LY135305 to inhibit spontaneous metastasis and to increase animal survival were evaluated. These compounds represent widely varied structures and were evaluated because they have been found to inhibit thromboxane synthetase, cyclooxygenase, and thrombin activation, respectively. These biochemical processes have been proposed in the literature as targets for antimetastatic drugs. The purpose of this investigation was twofold: (a) to compare the antimetastatic activities of the Eli Lilly compounds to those of the reference antimetastatic compounds nafazatrom and RA233, and (b) to examine the correlation between inhibition of spontaneous lung metastasis and survival. Spontaneous metastasis of the Lewis lung carcinoma was used to evaluate the antimetastatic activity of the compounds. In this model 5 x 10(5) tumor cells were implanted into the gastrocnemius muscle, the primary tumor was resected on Day 14, and metastatic lung lesions were counted on Day 25. Compounds were administered every 12 h on Days 5 through 19. Nafazatrom, LY150310, LY189332, and LY135305 were found to inhibit spontaneous lung metastasis in a dose-dependent manner. The ED50 values for the respective inhibitions with these compounds were 50, 0.5, 2, and 0.35 mg/kg/day; the respective therapeutic indexes (LD50/ED50) were 7, 180, 255, and 511. To evaluate the effect of nafazatrom, LY150310, LY189332, and LY135305 on animal survival, the compounds were given at maximally antimetastatic doses of 200, 60, 20, and 6 mg/kg/day, respectively. Two dosing schedules were used: (a) on Days 5 through 19 and (b) on Day 5 until death. Neither the median survival times nor the numbers of long-term survivors were significantly changed with any of the compounds at any dosing schedule. RA233, given to a maximally tolerated dose of 200 mg/kg/day on Day 5 until death, did not inhibit lung metastasis and did not increase median survival time. Postmortem examination of animals dosed with nafazatrom, LY150310, LY189332, and LY135305 showed complete inhibition in lung lesions and the appearance of lesions in the liver, kidney, spleen, and brain. The results of this investigation show that the effect a compound has on the number of metastatic lesions in a target organ may not be predictive of its effect on survival. To successfully translate laboratory data into the clinic, survival should be considered as a predictor of a compound's potential clinical utility.

Pulmonary gas trapping in the guinea pig and its application in pharmacological testing.

Airway constriction produced by bronchoconstrictive aerosols in vivo can result in substantial postmortem pulmonary gas trapping in the guinea pig. In order to use gas trapping responses for the evaluation of potential antiasthma agents, we developed a multiple animal inhalation exposure apparatus and an accurate system for quantitating excised lung gas volumes in the guinea pig. Aerosols of histamine, methacholine, and leukotriene D4 were shown to produce gas trapping responses that were inhibited in a dose-dependent fashion by appropriate antagonists. The approach described provides an objective and sensitive measure of the severity of airway obstruction, does not require surgery or anesthesia, and allows excellent control of unwanted sources of experimental variation.

The 20,000 dalton structural variant of recombinant DNA-derived methionyl human growth hormone has early insulin-like effects in hypophysectomized rats.

The 20,000 dalton variant of recombinant DNA-derived methionyl human growth hormone (20K-Met-hGH) induced decreases in blood glucose and free fatty acid concentrations one hour after intraperitoneal injection into fasted, hypophysectomized rats. Similar results were obtained using the 22,000 dalton form of recombinant DNA-derived methionyl human growth hormone (22K-Met-hGH). The data reported show that 20K-Met-hGH induces early insulin-like effects similar to the responses produced by 22K-Met-hGH in fasted hypophysectomized rats.

Metastatic spread of the PAIII prostatic adenocarcinoma after implantation in the tail of the rat.

The spontaneous metastatic spread of a suspension of PAIII prostatic adenocarcinoma cells from the tail site of implantation was analyzed over a period of 5 weeks in male Lobund-Wistar (LW) rats. Following subcutaneous injection of the PAIII cells, the tumor metastasized through the primary lymphatic drainage. PAIII microfoci were evident in the gluteal and iliac lymph nodes prior to colonization of the lungs. Growth of the primary tumor was evidenced by significant weight differences of the tails of PAIII-bearing and control rats 1 week after tumor implantation. Time-dependent sequential spread of the adenocarcinoma was quantitated. Significant differences were noted between PAIII-bearing and control animals with respect to the gluteal lymph node weights (+2 weeks), iliac lymph node weights (+3 weeks), dry lung weights, and lung colony numbers (+4 weeks) after tumor implantation. During the course of these studies, the whole blood prothrombin, activated partial thromboplastin, and recalcification times for the PAIII-bearing animals were similar to those of the control group. These findings indicate that there were no gross changes in systemic blood coagulation accompanying the metastasis of PAIII cells from the primary tumor. The tumor in LW rats produced a consistent pattern of growth and metastasis that is suitable for quantitation. The PAIII prostatic adenocarcinoma is a sensitive and reproducible system that may be useful to evaluate potential antimetastatic and cytotoxic agents for the treatment of hormone-insensitive prostatic cancer.

Hyperglycemic activity in dogs of recombinant DNA-derived 20,000 dalton variant of methionyl human growth hormone.

The recombinant DNA-derived 20,000-dalton variant of N-terminal methionyl human growth hormone (20K-Met-hGH) had a hyperglycemic effect in fasted dogs when injected 11 hours prior to an oral glucose tolerance test (OGTT). These results reported here suggest that 20K-Met-hGH can induce glucose intolerance in dogs similar to that produced by recombinant DNA-derived 22,000 dalton N-terminal methionyl human growth hormone (22K-Met-hGH) and the normal pituitary-source human growth hormone (22K-hGH).

Inhibitory effect of warfarin on the metastasis of the PAIII prostatic adenocarcinoma in the rat.

The PAIII rodent metastatic prostatic adenocarcinoma model was employed to evaluate the effects of dietary warfarin, a prototypic antagonist of thrombin generation on the lymphatic and pulmonary metastases of the tumor from the tail site of subcutaneous transplantation in male Lobund Wistar (LW) rats. In addition, the anticoagulant effects of warfarin were determined in the same animals. Warfarin, administered in the diet at concentrations equivalent to 0.063, 0.125 or 0.250 mg./kg. b.w. for 30 days had no effect on final body weight, gluteal or iliac lymph node weights. Significant (p less than 0.05) dose-dependent extensions of whole blood prothrombin (WBPT), activated partial thromboplastin (WBAPTT) and clotting times (WBCT) over control values were observed with warfarin treatment. Preliminary studies demonstrated that the 0.500 mg./kg. dose produced 50 per cent mortality at +14 days. Warfarin produced significant (p less than 0.05) dose-dependent decreases in the number of PAIII pulmonary metastases as indicated by reductions in dry lung weights and lung colony numbers when compared to untreated tumor-bearing controls. While the therapeutic index of warfarin is a limiting factor in clinical use as an antimetastatic agent, these results suggest that compounds capable of altering hemostatic mechanisms may be potential inhibitors of tumor metastasis. The PAIII prostatic adenocarcinoma model may be a useful system to quantitatively evaluate potential antimetastatic and cytotoxic agents.

Hemodynamic and electrocardiographic effects of fluoxetine and its major metabolite, norfluoxetine, in anesthetized dogs.

The cardiovascular effects of the selective serotonin uptake inhibitor, fluoxetine, and its N-desmethyl metabolite, norfluoxetine, were studied in anesthetized dogs during constant iv infusion of supratherapeutic doses (0.1 mg/kg/min for 50 min). Fluoxetine and norfluoxetine did not significantly affect mean blood pressure, pulmonary artery wedge pressure, or heart rate compared to a corresponding vehicle group. Cardiac output fell 15 to 20% during fluoxetine infusion due to nonsignificant decreases in both heart rate (10%) and stroke volume (5 to 10%). In contrast, the tricyclic antidepressant agent, amitriptyline, infused at the same dose, decreased both mean pressure and systemic vascular resistance (20%) and increased heart rate (20%). Pulmonary wedge pressure rose by 35%, and stroke volume fell by 20% suggesting impaired ventricular contractility. Both intramyocardial and infranodal conduction was slowed during amitriptyline infusion as indicated by increases in the QRS duration, and the PQ and HV interval. Fluoxetine and norfluoxetine had no influence on cardiac impulse conduction velocity as assessed by either surface or intracardiac conduction indices. Plasma concentrations of fluoxetine, norfluoxetine, and amitriptyline reached during infusion ranged from 1.0 to 2.5 micrograms/ml. Platelet [3H]serotonin uptake was inhibited by 95% during infusion of fluoxetine and about 75% during infusion of norfluoxetine or amitriptyline. These observations indicate that large iv doses of fluoxetine or norfluoxetine lack prominent cardiodepressant effects in dogs, suggesting a greater margin of safety for fluoxetine compared to tricyclic antidepressant drugs.