Log Dose-response Relationship Research Articles

T Wave Amplitude as a Quantitative Index of Regional Myocardial Sympathetic Responsiveness

Alterations in T wave morphology have been quantitated in seven open chest anesthetized dogs by simultaneous recording of electrograms from 10 epicardial sites across the anterior left ventricular wall under basal conditions, following left sympathetic stimulation (LSS) at 2, 4, 8, 12, and 16 Hz and during noradrenaline infusions (NAI) of 0.125, 0.25, 0.50, and 1.0 micrograms/kg/min. Overdrive atrial pacing at 175 beats/min was employed and rate of rise of left ventricular pressure (dP/dt) monitored. Linear log dose-response relationships were found between both peak T amplitude and left ventricular dP/dt for NAI between 0.125 and 0.50 micrograms/kg/min (peak T wave amplitude 4.0 +/- 0.9 to 1.4 +/- 0.7 mV). Following LSS, T wave amplitude responses were highly variable both between animals and between electrode sites in individual studies. A linear log dose-response relationship was found at stimulation frequencies between 8 and 16 Hz (T amplitude 3.9 +/- 1.4 to 1.8 +/- 1.2 mV). Changes in QT interval were minor and inconsistent. It is concluded that changes in peak T wave amplitude may provide a useful index of regional myocardial sympathetic responsiveness following NAI, but are more variable following LSS.

The utility of the macrophage migration inhibition test for invitro titration of tuberculins

The purpose of this study was to explore the fundamental principle of the potency estimation of tuberculins, as applied in vitro by the macrophage migration inhibition test (MIT) under agarose. The MIT was performed using specifically sensitized mouse and guinea-pig peritoneal macrophages and serial dilutions of the analogous PPD (purified protein derivatives of tuberculin) tuberculins as antigen. Statistical studies performed included (a) the standard deviation of the mean migration areas, (b) the analysis of variance, (c) the regression analysis, (d) its corresponding linearity test and (e) the determination of the related correlation coefficient. It was shown for the first time and in both animal species under study that there is correspondence between the log dose-response relationship of the tuberculin PPD in MIT under agarose and the well known in tuberculin cutaneous reaction. The MIT may therefore successfully replace the in vivo titration of tuberculins.

An improved bioassay method for determining natriuretic activity of atrial extracts

Extracts of mammalian atrial tissue contain potent natriuretic substances known collectively as atrial natriuretic factor (ANF). The purposes of the present experiments were: 1) to improve on existing bioassay methodology for the detection of ANF activity in atrial extracts, and 2) to compare the ANF activity of atrial extracts prepared from Brattleboro-stain diabetes insipidus (DI) rats with that from normal and water-deprived Long-Evans (LE) rats. A pool of atrial tissue extract (AE) was prepared from normal Sprague-Dawley rats for use as a standard against which unknown AE samples could be compared. Five doses, ranging from 27 to 432 micrograms of AE protein, were assayed in the Sprague-Dawley bioassay rats. Phosphate-buffered saline (PBS) vehicle and ventricular tissue extracts were also assayed. Statistical analysis of several log dose-response relationships revealed that the bioassay response most appropriate in determining relative natriuretic activity of AE was the log of the experimental/control ratio for sodium excretion. The bioassay was used to demonstrate that PBS atrial extracts from both water-deprived LE rats and DI rats contain more natriuretic activity than do PBS atrial extracts from LE rats.

Influence of extracellular Ca on the cyclic AMP production in the tooth pulp cells of rats

In our previous studies,the dentine calcification of rat incisor tooth was closely related to levels of cyclic AMP (cAMP) and Ca in the pulp3and parathyroid hormone (PTH) enhanced cAMP production in the tooth pulp cells. In the present study, influence of extracellular Ca on the cAMP production with PTH in isolated pulp cells was examined. Cells were isolated from upper and lower incisor pulp by collagenase digestion,and the cells were pre-incubated for 60 min at 37°C in Ca free HEPES-Hanks solution (pH 7.4). Then, isotonic PTH, Ca(as CaCl2) and/or A23187 was added to the incubation media,and cAMP production was measured in short time intervals. The results were as follows: 1) In the presence of PTH (0.1 U/ml), addition of Ca ranging from 0.2 to 2.5 mM caused a marked increase in cAMP production within 2.5 min. The rise in cAMP was proportional to the concentration of Ca added and reached to a peak at 2.5 mM, then declined at higher Ca level. A simultaneous addition of 2 mM EGTA to the same media shifted the above :eak to higher Ca level at 4.5 mM. 2) In the Ca-containing media (2.5 mM la), log dose-response relationship between cAMP production and added PTH 0.1 to 1.0 U/ml) showed a good linear rise in cAMP, which was two times greater than that of Ca-free media. 3) In the presence of Ca (2.5 mM), an addition of 10 A23187 (Ca ionophore) showed two-fold increase in cAMP production. A simultaneous addition of A23187 and PTH caused 3.6-fold increase in cAMP. The above two agents acted additively to each other on cAMP production. These results suggest that extracellular Ca in the dental pulp ■ay be important in cAMP production with PTH.

The rat isolated stomach sheet; an in vitro model for the study of the physiology and pharmacology of gastric acid secretion

The development of an isolated stomach preparation from immature rats is described. Acid secretion was measured by titration of mucosal samples taken at 15 min intervals. Nonstimulated acid secretion was generally in the range 60–180 μmol H +g −1 wet weight of mucosa hr −1 and was maintained for up to 5.5 hr. A small proportion of stomachs (20%) had a higher level of spontaneous secretion which fell to the more usual low level within 1.5 hr. Pentagastrin (1.3 × 10 −8 M-1.3 × 10 −7 M), bethanechol (2 × 10 −6 M-3 × 10 −5 M), histamine (5 × 10 −6 M-5 × 10 −4 M) and theophylline (2 × 10 −4 M-1 × 10 −3 M) induced concentration-dependent stimulation of acid secretion. Linear log-dose response relationships were obtained for each of the four stimulants. The regression coefficients from each drug study, calculated over a similar increase in concentration, were not significantly different from one another. The maximal secretory rates recorded with the four secretagogues were comparable, range 152.5–226.0 μmol H +g −1hr −1. The methodology and results are compared with other mammalian in vitro stomach preparations currently used to study the physiology and pharmacology of gastric acid secretion.

Dose-response relationships for spironolactone at steady state.

The overnight urine electrolyte and plasma potassium responses to spironolactone (25, 50, 100, and 200 mg daily) at steady state were investigated in 11 healthy subjects after fludrocortisone challenge. For sodium excretion and urine log10 10 Na/K, log dose-response relationships were defined (P less than 0.001 in each case), but there was little evidence of dose-related influences on potassium excretion or plasma potassium. The findings confirm the limitations of the fludrocortisone model in evaluating the potassium-sparing properties of aldosterone antagonists at steady state and of the urine sodium; potassium ratio as an overall index of renal antimineralocorticoid activity.

Comparison of the pulmonary, hepatic and renal extraction of PGI 2 and 6-KETO-PGE 1

Prostaglandin (PG)I 2 and 6-keto-PGE 1 were infused into the aortic, arch, femoral vein, renal artery and portal vein in anestized dogs over a dose range to produce aa stable decrease in systemic blood pressure after 7 min of infusion. Mesenteric artery blood flow was measured continously with a non-cannulating electromagnetic flow probe. Parallel log dose-response relationships were seen for decreases in blood pressure and increases in mesenteric blood flow with both prostaglandins when infused into the aortic arch. The dose responses for intra-aortic and intra-aortic and intravenous infusion of PGI 2 were not different shifted to the right with intrarenal and intraportal infusions. With 6-keto-PGE 1 the dose responses after intravenous, intrarenal and intraportal infusions were all shifted to the right. By comparing doses which reduced blood pressure by 10 mm Hg, the extraction of the PGs by the lungs, kidney and liver was calculated. PGI 2 had no significant pulmonary extraction, 31% renal and 75% hepatic extraction. In contrast, 6-keto-PGE 1 had extractions of 40, 66 and 51% for pulmonary, renal, and hepatic vascular beds, respectively. We conclude that 6-keto-PGE 1 is reasonably well extracted by the lungs, kidney, and liver.

Reversible swelling evoked by epinephrine, 8-bromo-cyclic 3′,5′-guanosine monophosphate and feeding in the mast cells of the rat

Swelling, shape distortion, and sectorially decreased granule population-density can be observed in rat-mesentery mast cells exposed to epinephrine in vivo or in vitro. To a lesser degree, such changes are also noted in mast cells of untreated rats. Changes due to epinephrine were quantified both in mesentery spreads and in fixed and photographically magnified isolated rat peritoneal-fluid mast cells. Threshold effectiveness of epinephrine was 0.5 μg/kg in vivo (i.v.) and 10 −8 moles/liter in vitro. Rapidity, partly linear log dose-response relationships, and reversibility characterize the responses of mast cells to epinephrine. Within limits, re-exposure to epinephrine of spontaneously deactivated mast cells resulted in renewed change. N 6-2′- O-Dibutyril-cyclic 3′,5′-adenosine monophosphate (diBu-cAMP) inhibited, and 8-bromo-cyclic 3′,5′-guanosine monophosphate (8-Br-cGMP) reproduced, the effects of epinephrine; like the catecholamine, neither cyclic nucleotide derivative caused a release of histamine or a degranulation of mast cells in the manner that compound 48 80 was shown to do. A return to normality of mesenteric mast cells of 48 80 - treated rats required between 24 and 48 hr; in the epinephrine-treated rat, this return was complete within 60 min. Feeding significantly increased the number of morphologically altered mast cells present in mesenteries of 24 hr-fasted rats. A renewed fast reduced altered mast cell numbers to prefeeding levels. Although mast cell alterations evoked by feeding appeared to be morphologically similar to those caused by epinephrine or 8-Br-cGMP, the catecholamine cannot be the mediator of such changes because phenoxybenzamine, an α-adrenergic blocking agent, prevented the effect of epinephrine but not that of feeding on mast cells.

Effect of prolactin and prostaglandins on the stimulation of prolactin binding sites in the male rat liver

Induction of prolactin hepatic receptors in the male rat by exogenous prolactin and the possible involvement of prostaglandins in this process were studied. When ovine prolactin 500 μg/kg was administered sc in saline containing 10% PVP (polyvinylpyrrolidone), twice daily for 6.5 days and the rats killed 48 h after the last injection, the specific binding of 125I-labelled ovine prolactin to prolactin hepatic receptors was raised 26-fold, while administration of prolactin in saline only caused a 7-fold increase. A well correlated log dose-response relationship was demonstrated between 12.5 and 500 μg of prolactin in saline-PVP, with the lowest dose causing an 18-fold increase in binding. A shorter 4.5 day treatment of prolactin in saline—PVP caused only a small 3-fold increase in prolactin binding. Scatchard analysis showed that these increases resulted from increases in receptor concentration. The effect of prolactin on the induction of the hepatic receptors could not be mimicked by PGE 1, PGE 2 or PGF 2α, nor could PGF 2α synergize with a short treatment with prolactin. Further, indomethacin caused no significant effect on this action of prolactin. It seems that prolactin does not induce its own receptors in the rat liver by stimulation of prostaglandins in this tissue.

The effect of gamma-aminobutyric acid on the input conductance and membrane potential of Ascaris muscle.

1 Twin intracellular recordings were made from the bag region of Ascaris muscle in order to make conductance measurements. The preparation was bathed in a cool (22 degrees C) Ringer solution to abolish the large spontaneous depolarizing potentials and to improve stability for recording.2 The resting membrane potential was -31 +/- 1 mV, mean +/- s.e. mean (n = 17). The current-voltage plots were linear in the hyperpolarizing direction but showed evidence of delayed rectification during the application of depolarizing currents. The input conductance of the bag was measured from the slope of these plots during the application of hyperpolarizing current. The resting conductance of the bags was 2.4 +/- 0.2 muS, mean +/- s.e. mean (n = 12).3 When the preparation was perfused with gamma-aminobutyric acid (GABA) in concentrations greater than 3 muM, a dose-dependent increase in conductance associated with a hyperpolarizing potential was recorded. The log dose-response relationship obtained from 6 preparations was sigmoidal and had an ED(50) of 13 muM.4 When Cl(-) in the Ringer was replaced by SO(4) (2-), the GABA-induced conductance changes decreased and were associated with depolarizing potentials.5 Voltage responses were recorded in the bag region during the iontophoretic application of GABA to different regions of the muscle cell. The largest responses were recorded when GABA was applied to the bag region. Smaller responses were recorded when GABA was applied to the arms and syncytial regions. The responses of the bags were dose-dependent and were antagonized by bath-applied picrotoxin.6 An extrapolation method using 10(-5) M GABA suggested that the GABA reversal potential was about 30 mV more negative than the resting membrane potential. This was confirmed by means of a two microelectrode voltage clamp technique. The reversal potential was thus estimated as -61.2 +/- 2.2 mV mean +/- s.e. mean (n = 27).

Dose–Response and Plasma Concentration–Response Relationships of Pancuronium in Man

The dose-response and plasma concentration-response relationships for pancuronium in man were studied during its intravenous administration to eight patients at a rate of 1.62 microgram/kg/min. The (log) dose-response relationships resulted in a sigmoid curve that was linear in its central range. At 20, 50 and 80 per cent paralysis the cumulative dosages (mean +/- SEM) were 0.04 (+/- 0.01), 0.06 (+/- 0.01), and 0.08 (+/- 0.02) mg/kg, respectively. Administration of pancuronium, 56 microgram/kg, to another 12 patients at a more rapid rate resulted in a maximum intensity of blockade of more than 50 per cent. The (log) plasma concentration-response curve was not parallel to the dose-response curve, with mean (+/- SEM) concentrations at 20, 50 and 80 per cent paralysis of 0.21 (+/- 0.04), 0.25 (+/- 0.04), and 0.30 (+/- 0.04) microgram/ml, respectively during the onset of paralysis. Following cessation of the infusion, plasma concentrations of pancuronium were usually lower for the same intensity of paralysis. Using data for the entire response range during recovery from paralysis, the mean effective plasma concentration of pancuronium for a 50 per cent response was 0.20 microgram/ml. Recovery from blockade to 95 per cent paralysis (5 per cent of control twitch height) was associated with a plasma concentration of 0.25 microgram/ml, a value in agreement with plasma concentrations obtained following a single bolus administration of pancuronium, 6 mg, to 30 patients. For 27 patients the rate of decline of paralysis from 80 to 20 per cent showed a highly statistically significant relationship to the apparent rate of decline in the plasma concentrations of pancuronium.

SHORT-TERM REGULATION OF LH AND FSH SECRETION IN CYCLIC WOMEN

ABSTRACT The effects of two consecutive LH-RH injections at 120 min intervals with either a varying first or second LH-RH dose on pituitary gonadotrophin response were investigated in 15 eugonadal women to study pituitary secretory processes. Each volunteer underwent a total of 4 LH-RH double stimulation tests. In group I (n = 8) the first LH-RH dose of each of the 4 tests was fixed at 25 μg, whereas the second LH-RH dose consisted of either 6, 25, 100 or 400 μg. In group II (n= 7) the first LH-RH dose varied between 6 and 400 μg, while the second LH-RH dose was kept constant at 25 μg. Serum gonadotrophin and serum ovarian steroid levels were determined by radioimmunoassay before and after LH-RH administration. The volunteers in both groups served as their own controls. A linear log-dose response relationship was found between the various doses of LH-RH injected and the corresponding LH and FSH elevations elicited. However, the dose of the first LH-RH injection also significantly influenced the gonadotrophin reaction after the second LH-RH injection in a linear log-dose response relationship. Serum levels of oestradiol, 17-hydroxyprogesterone and progesterone significantly increased in response to the elevated serum gonadotrophin levels after LH-RH stimulation during the 4 h test period, but the rise did not correlate to the LH-RH dose used. The results indicate that LH-releasing hormone stimulates not only the release, but also the synthesis of LH and FSH in a dose-related manner. These findings are consistent with our previously reported concept that the magnitude of LH and FSH response to the first LH-RH injection reflects the "storage capacity", while the increase observed after the second LH-RH injection represents the "synthesis capacity" of the gonadotrophs.

Differential response of early erythropoietic and granulopoietic progenitors to dexamethasone and cortisone.

The sensitivity of erythropoietic (BFU-E) and granulopoietic (CFU-C) progenitor cells to dexamethasone and cortisone was studied in cultures of mouse bone marrow. Although the log dose-response relationships had a similar form, the BFU-E were much more sensitive than the CFU-C to either glucocorticoid. The dexamethasone concentration for 50% inhibition was 3 X 10)-9) M for BFU-E and 60 X 10(-9) M for CFU-C. The differential sensitivity to cortisone was even greater, with 60% inhibition of BFU-E and 18% inhibition of CFU-C at 0.1 microgram/ml. These findings suggest a specific rather than a general response to glucocorticoids and indicate that granulocyte-macrophage progenitors are less affected than early erythroid progenitors by physiologic concentrations of these hormones.

A comparison of the pulmonary, renal and hepatic extractions of PGI 2 and PGE 2 - PGI 2 a potential circulating hormone

Prostaglandin (PG) I 2 and PGE 2 were infused into the aortic arch, femoral vein, renal artery and portal vein in anesthetized dogs over a dose range to produce a steady decrease in systemic blood pressure after 10 mins infusion. Parallel log dose-response relationships were observed with both PGI 2 and PGE 2. PGE 2 was a more potent depressor than PGI 2 when infused into the aortic arch. The doses to reduce blood pressure by 5 mm Hg were used to calculate the extraction of the compounds by the lungs, kidney and liver. The pulmonary extraction of PGE 2 was 96 ± 2% and was essentially complete following combined pulmonary and renal or pulmonary and hepatic extraction. In contrast, there was no significant pulmonary extraction of PGI 2. Combined renal and pulmonary extraction was 43 ± 11% and combined hepatic and pulmonary extraction 87 ± 5%. These results indicate a marked difference in the organ metabolising capacity for PGE 2 and PGI 2. Since PGI 2 has been shown to be produced both in the kidney and stomach it is possible that PGI 2 produced endogenously could pass into the circulation and exert systemic pharmacological effects.

Estimation of plasma half-lives of vasopressin analogs from vasopressor responses by curve-fitting.

SummaryVasopressor responses by rats to graded doses of AVP, dAVP, and AVT were analyzed in an attempt to find a method for estimating plasma half-life from responses. The resulting “curve-fit” method indicated half-lives of 2.6 ± 0.3, 4.0 ± 0.3, and 9.2 ± 1.4 min for AVP, AVT, and dAVP, respectively, after single intravenous injections. The half-lives of two peptides can be compared in one rat the “curve-fit” method. This method can also provide useful information concerning the relative contributions of the plasma half-life, the log dose-response relationship, and other factors, to the duration of the response.

AGONIST AND ANTAGONIST PROPERTIES OF BUPRENORPHINE, A NEW ANTINOCICEPTIVE AGENT

1. Buprenorphine is a highly lipophilic derivative of oripavine. In rodent antinociceptive assays (writhing, tail pressure), buprenorphine had an action which was rapid in onset and of long duration; it was 25-40 times more potent than morphine after parenteral injection and 7-10 times more potent after oral administration. 2. The log dose-response relationship for buprenorphine was curvilinear in mouse and rat tail flick tests with the antinociceptive effect decreasing at higher, non-toxic doses. 3. Tolerance developed to the antinociceptive activity of buprenorphine in mice. 4. No signs of abstinence were observed on naloxone challenge or after abrupt withdrawal in monkeys receiving buprenorphine chronically for one month. 5. Buprenorphine antagonized the antinociceptive actions of morphine in mouse and rat tail flick tests but was an ineffective antagonist in the rat tail pressure test. 6. Buprenorphine precipitated signs of abstinence in morphine-dependent mice and monkeys but not in morphine-dependent rats. 7. Buprenorphine produced Straub tails in mice. This effect was not antagonized when the animals were pretreated with naloxone. However, in the rat tail pressure test high doses of diprenorphine antagonized established antinociceptive effects of buprenorphine. 8. It is concluded that buprenorphine represents a definite advance in the search for a narcotic antagonist analgesic of low physical dependence potential.

A Superfusion System Technique for the Study of the Sites of Action of Glucocorticoids in the Rat Hypothalamus- Pituitary-Adrenal Systemin Vitro. I. Pituitary Cell Superfusion

Rat anterior pituitary cells were placed in a superfusion column and were stimulated by rat hypothalamic extract. The rate of ACTH secretion was monitored by collecting fractions eluting from the column every 2 min. Dispersed rat adrenocortical cells were used to determine the amounts of ACTH in the superfusate. ACTH appeared in the medium 6-12 sec after stimulation of the cells. A linear log dose-response relationship existed between 1/8 to 1 rat hypothalamus extract and the amounts of ACTH released. Repeated pulses of CRF stimulation of the same column of pituitary cells resulted in repeated, identical peaks of ACTH. Constant stimulation caused a plateau in hormone release that lasted as long as the stimulus was present. The stimulated, but not the basal ACTH release, could be inhibited by superfusion with corticosterone in vitro (0.2 mug/ml), or by treating the pituitary donor animal in vivo with corticosterone (5 mg/100g BW), cortisol or dexamethasone. Adrenalectomy of the donor animal caused increases in the basal and the stimulated ACTH release.

Relative Activities of Some Metabolites and Analogs of Cholecalciferol in Stimulation of Tibia Ash Weight in Chicks Otherwise Deprived of Vitamin D

Nine metabolites and analogs of cholecalciferol (CC) were tested for ability to increase tibia ash weight in chicks otherwise deprived of vitamin D. All of the compounds promoted bone mineralization in a linear log dose-response relationship. The maximal response obtained for any compound was an approximate doubling in bone ash weight compared to vehicle-treated controls. Relative potencies, based upon the calculated ash weight doubling dose, were as follows: 1 alpha, 25-(OH)2-CC = 1 alpha-OH-CC greater than CC greater than 25-OH-CC greater than 24R, 25-(OH)2-CC = 1 alpha,24R, 25-(OH)3- CC greater than 5,6-trans-25-OH-CC greater than 1 alpha, 24S, 25- (OH)3-CC greater than 5,6-trans-CC greater than 24S, 25-(OH)2-CC.

The stimulation of corticosteroidogenesis in the interrenal of the elasmobranch Dasyatis sabina by mammalian ACTH

1. The interrenal tissue of Dasyatis sabina responded in vitro to the presence of mammalian ACTH by an increased release of steroid. 2. The steroid released in response to stimulation by mammalian ACTH had the mobility of l α-OH-corticosterone which is the normal product of the elasmobranch interrenal in vivo or when stimulated in vitro by elasmobranch pituitary homogenates. 3. The response of the elasmobranch interrenal to mammalian ACTH is dose dependent with a linear log dose-response relationship.

Induction of luteinizing hormone (LH) release and ovulation in rats, hamsters, and rabbits by synthetic luteinizing hormone-releasing factor (LRF).

The efficacy of synthetic LRF in inducing LH release in the estrogen progesteroneblocked, chronically ovariectomized rat and ovulation in the cycling rat, hamster, and rabbit was established. Synthetic LRF was highly effective by various modes of administration, but there were differences in the time course and magnitude of the LH release response depending on the route, and differences in the quantity of LRF required to induce ovulation depending on the species. Following the intracarotid injection of LRF, serum LH peaked at 10 min and a linear log dose—response relationship was obtained over the range of 1 to 5O ng per rat. After the oral administration of 1 mg of LRF, serum LH concentrations were increased to a maximum (27– fold) by 30 min, then steadily declined, reaching basal levels by 90 min. A sustained effect of LRF (10 or 100 μg/rat) on LH secretion was noted following intravaginal dosing using a repository vehicle; serum LH was significantly increased by 10 min, maximal at 30 min, and remained elevated for at least an additional 90 min. LRF, given sc in μg quantities or orally in mg amounts, induced ovulation in chlorpromazine (CPZ)—blocked proestrous rats. The lowest sc dose of LRF yielding 100% ovulation (MED100) in the CPZ—blocked proestrous rat was 1 μg (3.7 μg/kg body wt) whereas in the phenobarbital—blocked proestrus hamster the MED100 was 0.01 μg (0.11 μg/kg body wt). In estrous rabbits, an iv dose of 2.5 μg of LRF (0.88 μg/kg body wt) was the MED100 for induction of ovulation, a value intermediate to that of the rat and hamster. The administration of pharmacological doses (1000 times or more the MED100) to cycling rats, hamsters, or rabbits at a time coincident with the endogenous surge of ovulating hormone failed to induce superovulation. These results demonstrate that synthetic LRF is highly efficacious by several routes of administration in stimulating LH release and ovulation in three rodent species. (Endocrinology92: 1515, 1973)