Pharmacokinetics and biological actions of subcutaneously administered human brain natriuretic peptide.

Human brain natriuretic peptide (hBNP) has demonstrated favorable hemodynamic effects in patients with congestive heart failure; however, the peptidic nature of this compound has focused clinical testing on protocols involving intravenous delivery. We have studied subcutaneous delivery as an alternative method of administering hBNP. Administration of 30 microgram/kg hBNP by either subcutaneous or intravenous delivery protocols resulted in significant hBNP-immunoreactive material in the plasma with area under the plasma concentration-time curve values of 310 +/- 20 nmolxmins/liter and 187 +/- 47 nmolxmins/liter, respectively. Plasma cyclic GMP, a surrogate marker of activation of the biological receptor for hBNP, was elevated for a longer period of time following subcutaneous delivery compared with intravenous delivery. Subcutaneous delivery of 30 microg/kg hBNP resulted in natriuresis, diuresis and reduced systolic blood pressure in anesthetized normotensive rabbits, effects similar in magnitude yet prolonged in duration compared with those elicited by the same dose of hBNP delivered intravenously. Systolic blood pressure following hBNP treatment remained below base-line values for 50 and 150 min following intravenous and subcutaneous delivery protocols, respectively. These results suggests that subcutaneous delivery of hBNP may be a viable therapeutic alternative to intravenous modes of delivery.

Human brain natriuretic peptide reduces blood pressure in normotensive and acute norepinephrine-induced hypertensive rabbits.

Human brain natriuretic peptide (hBNP) is a cardiac-derived peptide hormone with potent hemodynamic and renal effects in dogs, monkeys, and humans, but not in rats. At present there is no small animal model to study the actions of hBNP. These studies describe the effects of hBNP in New Zealand White rabbits in normotensive and acute norepinephrine-induced hypertensive states. Intravenous administration of hBNP (1, 3, 10, and 30 microg/kg) to anesthetized rabbits resulted in a dose-dependent diuresis and natriuresis and a decrease in systolic blood pressure. Bolus administration of hBNP resulted in a time- and dose-dependent accumulation of plasma cyclic GMP, consistent with activation of a particulate guanylyl cyclase receptor. The hemodynamic actions of hBNP suggest clinical utility for the management of acute hypertension associated with numerous surgical procedures, a condition linked to catecholamine activation. In rabbits with norepinephrine-induced acute hypertension, bolus and continuous infusion of hBNP markedly reduced blood pressure. These studies demonstrate that the rabbit is a useful species to study the hemodynamic and renal effects of hBNP and that this peptide may have therapeutic utility for the acute reduction of hypertension associated with catecholamine activation.

Use of reflectance spectrophotometry in the human corticosteroid skin blanching assay.

A reflectance spectrophotometric method for evaluation of the skin blanching response to topical corticosteroids was evaluated. This blanching response is used, for drug development and regulatory purposes, to assess potency and bioequivalence of topical corticosteroid products. The common method involves the use of a human rater to measure blanching response in the skin. This study evaluated an instrumental alternative to the human rater and used this method to measure the differences between a number of brand name and generic topical corticosteroid products (six creams and six ointments). Products were applied to the forearms of normal volunteers and the blanching responses were assessed after 6 and 16 hours in both occluded and non-occluded skin sites. Only the fluocinolone acetonide generic and brand name preparations were different from each other. The spectrophotometric method proved to be equivalent but not superior to the standard human observer method.

Transcutaneous chemical collection of caffeine in normal subjects: relationship to area under the plasma concentration-time curve and sweat production.

A novel transcutaneous chemical collection device (TCD) has been developed to study the phenomenon of outward transcutaneous chemical migration. The TCD is a Bandaid-like device containing an immobilized aqueous media and binding reservoir material to prevent back-transfer into the skin. This device, when placed against the skin, allows collection and quantitation of chemicals that diffuse directly through the skin from within the body. The relationship of the amount of drug collected in the TCD to the amount in the body available for collection (as represented by the area under the plasma-concentration time curve, AUC) and the effects of sweating, a potential confounding factor, on collection of drug in a TCD were studied, using caffeine as a model compound. TCD were placed on the skin of normal male volunteers. Twenty-four hours later subjects took caffeine by mouth. Blood samples were collected and TCD were removed at various times after drug intake and analyzed by HPLC for caffeine. Studies of the sweating effect were carried out in a similar manner, except that one arm of each subject was maintained at 40 degrees C to induce local sweating, the other arm acted as a non-sweating control. The amount of caffeine collected was linearly related to the AUC. Sweating seemed to have a large (40%) contribution to transdermal collection in the early period (5.5 h) of the study, but this difference was much less (14%) at longer collection times (10 h).

Noninvasive transdermal chemical collection. II. In vitro and in vivo skin permeability studies.

In vitro and in vivo skin permeability studies were conducted to investigate properties of several candidate transdermal chemical collection devices (TCDs). The TCD consists of a binding reservoir of activated charcoal suspended in a gel medium which is occlusively placed in direct contact with the skin. Binding of three model compounds (theophylline, methotrexate, and parathion) was studied in hydrophilic (agarose or PVA/PVP) and lipophilic (silicone) gel/carbon compositions. The effects of gel composition, compound hydrophilicity/lipophilicity, and hydration of skin on quantity of transdermally collected chemical and 'apparent' permeability were investigated using a 'fuzzy' rat animal model. In vitro and in vivo apparent permeability coefficients (Kp; cm/h) for amphophilic theophylline (6.95 x 10(-4) and 8.34 x 10(-4), respectively) and hydrophilic methotrexate (3.5 x 10(-3) and 3.2 x 10(-4), respectively) using an agarose aquagel TCD were greater than the corresponding Kp values obtained when silicone lipogel TCDs were employed (0.3 x 10(-4) and 3.2 x 10(-4), respectively, for theophylline; no measurable methotrexate was collected). Occlusive hydration of skin profoundly increased permeability of the hydrophyilic model compound, methotrexate. In vivo Kp values for lipophilic parathion were greater with a silicone TCD (6.7 x 10(-4) than with an agarose TCD (3.8 x 10(-4). We conclude that it is possible to influence transdermal chemical collection through modifications in the gel composition and by hydration of the skin.

Transcutaneous collection of theophylline: constancy and linearity of skin permeability.

Transcutaneous chemical collection is a novel method for noninvasive collection and measurement of body exposure to chemicals using a transcutaneous collection device (TCD) consisting of a circular adhesive-tape-encased saline-activated carbon-aquagel patch. The objectives of this study were to determine (1) the time-course of skin permeability change after the placement of a TCD on the skin, and (2) the relationship between the amount of theophylline collected in a TCD and the amount of theophylline in the body as expressed by the area under the plasma concentration-time curve (AUC). Skin permeability changes were determined by emplacing TCDs (24/monkey) on the chests and abdomens of female rhesus monkeys (12 studies in 4 monkeys) at 48, 24, 6, 3 and 1 h prior to dosing with aminophylline (10 mg/kg of theophylline, i.v.) over 30 min. Several blood samples were collected, and TCDs were removed at 24 h post-dose; samples were assayed for theophylline by HPLC. The apparent permeability coefficients (Kp) increased following TCD placement reaching 90% of maximum by 17 h. The relationship between the amount of theophylline collected in the device (Q) and amount in the body over time was determined by emplacing TCDs on rhesus monkeys (8 studies in 4 monkeys) 24 h prior to administration of 10 mg/kg of theophylline. Qs from the TCDs removed at 0.17, 0.5, 1, 3, 6 and 24 h were linearly related to the plasma AUC according to the relationship: Q = (A x Kp) x AUC, where A is the area of gel in contact with the skin for each TCD.

Outward transcutaneous chemical migration: implications for diagnostics and dosimetry.

Chemical substances migrate outwards from within the body to the skin surface by diffusion from cutaneous capillaries across the epidermis. Heretofore, study of transepidermal chemical emissions have been restricted to substances which are in the vapor phase at skin surface temperature. We have investigated outward transcutaneous chemical migration of nongaseous chemicals by devising an occlusive transcutaneous chemical collection system, consisting of a tape-encased plug of gelled saline in which activated carbon is dispersed. Investigations of nine chemicals in 'fuzzy' rats, rhesus monkeys, and man provide data which are consistent with a general theory of outward transcutaneous chemical migration. This noninvasive continuous transcutaneous sampling technique provides a new method for investigating skin permeability in vivo and may provide a basis for convenient diagnosis and monitoring of chemical exposure.

Opioid effects on plasma concentrations of luteinizing hormone and prolactin in the adult male rhesus monkey.

The role of endogenous opioid peptides (EOP) in the neuroendocrine control of primate gonadotropin and PRL secretion was studied in nonrestrained adult male rhesus monkeys. Morphine (0.5-1.0 mg/kg) was used as the prototype opiate, beta-endorphin (beta-END; 10-20 micrograms/kg) and [D-Ala2,D-Leu5] enkephalin (DADLE; 5-20 micrograms/kg) were used as representatives of EOP, and naloxone (0.5-2.0 mg/kg) was used as an opiate receptor blocker. Drugs were administered and blood was collected (at 20-min intervals for 4 h) through an indwelling jugular catheter. LH and PRL levels were measured in plasma by RIA. Intravenous administration of morphine (1.0 mg/kg) and DADLE (10 micrograms/kg) produced decreases in LH levels of 64% and 40%, respectively. These decreases occurred within 1 h after drug injections and lasted for approximately 3 h. beta-END had no effect on LH levels. Naloxone, at all doses studied, significantly increased LH levels (5- to 8-fold). The LH rises occurred within 20 min and lasted for up to 2 h. Both morphine and beta-END produced immediate increases in PRL, which remained elevated for 3 h. DADLE did not alter PRL levels. Naloxone (1.0 and 2.0 mg/kg) decreased PRL concentrations (45% and 60%, respectively). Pretreatment with morphine or DADLE did not alter the LH response to GnRH (100 micrograms) stimulation, indicating a hypothalamic site of action for the opioid inhibition of LH release. Naloxone administration reversed the inhibitory effects of morphine and DADLE on LH. The stimulatory effect of morphine on PRL levels was also reversed by naloxone. These studies further define the postulated physiological role of EOP in primate reproductive neuroendocrinology. Based on receptor selectivities of these opioid agonists, the inhibition of LH may be mediated by delta-receptors, whereas PRL release appears to be mu-mediated.

The role of endogenous opioid peptides in the control of androgen levels in the male nonhuman primate.

Plasma androgen levels studied following the injection of the opioid agonists morphine sulfate (0.5-1.0 mg/kg), beta-endorphin (10-20 mg/kg), and [D-Ala2, D-Leu5]-enkephalin (DADLE; 5-20 micrograms/kg), and the opioid receptor antagonist naloxone (0.5-2.0 mg/kg) in nonrestrained adult male rhesus monkeys. Drugs were administered and blood samples were collected through indwelling jugular catheters. Morphine (1.0 mg/kg) and DADLE (10.0 micrograms/kg) decreased androgen levels by 70% and 34%, respectively. Significant decreases occurred 80 minutes after drug injections, and levels remained depressed for 180 minutes; beta-endorphin (20 micrograms/kg) produced no effect on androgen levels. Treatment with naloxone (0.5 mg/kg-2.0 mg/kg) alone produced marked increases in androgen levels. Peak hormone levels occurred 80 minutes after naloxone administration and remained elevated for up to 2 hours. The depressant effects of morphine and DADLE on androgen levels were completely reversed by the administration of naloxone (1.0 mg/kg). In monkeys pretreated with hCG, neither morphine (1.0 mg/kg) nor DADLE (20 micrograms-kg) had any effect on androgen levels for up to 3 hours after opioid administration. Administration of morphine or endogenous opioid peptides exerts negative effects on androgen levels, whereas antagonism or endogenous or exogenous opiates by naloxone results in increases in circulating androgens. These results support a physiologic role of the endogenous opioid peptides in primate reproductive function.

Tolerance develops to the disruptive effects of delta 9-tetrahydrocannabinol on primate menstrual cycle.

Long-term exposure of sexually mature female rhesus monkeys (Macaca mulata) to thrice weekly injections of delta 9-tetrahydrocannabinol resulted in a disruption of menstrual cycles that lasted for several months. This period was marked by an absence of ovulation and decreased basal concentrations of gonadotropin and sex steroids in the plasma. After this period, normal cycles and hormone concentrations were reestablished. These studies demonstrate that in rhesus monkeys subjected to long-term treatment with delta 9-tetrahydrocannabinol tolerance develops to the disruptive effects of the drug on the menstrual cycle.

The effects of marijuana extract and delta 9-tetrahydrocannabinol on luteal function in the rhesus monkey.

The effects of marijuana extract (ME) and delta 9-tetrahydrocannabinol (THC) on corpus luteum function were studied in the rhesus monkey by the use of in vivo and in vitro techniques. THC (2.5 mg/kg) or vehicle (3% Tween 80 in saline) was administered by an intramuscular injection to rhesus monkeys on day 20, 21, or 22 of the menstrual cycle. Progesterone (P) levels were measured at 6-hour intervals for the first 24 hours after treatment. THC caused a significant decrease in P levels during this 24-hour period. This decrease was reversed by the administration of human chorionic gonadotropin (hCG) at 6 hours after THC administration. When THC was administered 2 hours after hCG, it failed to inhibit the expected rise in serum P levels caused by hCG. Direct effects of the drugs on P production were studied with the use of dispersed luteal cells obtained from monkeys on day 21 or 22 of the menstrual cycle. Neither ME nor THC had any effect on basal P production in these in vitro studies. These data suggest that the inhibitory effect of THC on P levels during the luteal phase are not mediated by a direct effect of the drug on ovarian steroid production.