Effects of hypophysectomy on some osmoregulatory parameters of the catfish, Heteropneustes fossilis (Bloch)

The catfish, H. fossilis, survives for long periods after hypophysectomy, although with impaired osmoregulatory mechanisms. Plasma osmolarity and cortisol levels decline significantly within 2 hr after hypophysectomy and attain the lowest values by about 27 hr. Hypophysectomy also results in a marked decrease in urine flow rate principally due to reduced glomerular filtration. The reduction in the ability of the kidney of hypophysectomized catfish to eliminate water results in hyperhydration of blood and muscle. Urine osmolarity and sodium concentration increase due to reduced tubular reabsorption of sodium. There is, however, no net change in the total urinary sodium loss. The catfish survives in fresh water after hypophysectomy presumably because its tissues can tolerate significant dilution of the body fluids.     

The pituitary gland mediates acute and chronic pain responsiveness in stressed and non-stressed rats.

The effect of hypophysectomy on the responsiveness of rats to acute (hot plate test) and chronic (formalin test) pain was studied. Hypophysectomy did not alter hot plate behavior but increased the duration of the paw withdrawal in the formalin test. Pre-exposure of rats to immobilization stress caused a transient yet significant increase in escape latencies from a hot plate as well as a significant decrease in the duration of paw withdrawal in the formalin test. Hypophysectomy blocked the effect of stress on these behavioral manifestations of acute and chronic pain. The effect of hypophysectomy was not reversed by adrenocorticotropin pretreatment. These results suggest that centrally acting pituitary hormones may have a requisite function in normal and adaptive pain control in mammals.     

Pineal and pituitary involvement in the photoperiodic regulation of body weight, coat color and testicular size of the Djungarian hamster, Phodopus sungorus

Hypophysectomy of 40-day-old male hamsters kept under long photoperiods resulted in a change in coat color from the brownish summer coat to the whitish winter coat, within 5 wk of the surgery, cessation of growth, and, most frequently, an additional loss in body weight. The testes of the hypophysectomized animals were involuted within 14 days after surgery. Continuous substitution of prolactin by implantation of two anterior pituitaries under the kidney capsule was able to reverse partly or totally the inhibitory effects of hypophysectomy on coat color and body weight, although there was no influence on testicular volume. The same effects could be achieved by daily s.c. injections of prolactin (100 micrograms ovine-PRL/day) into hypophysectomized hamsters, whereas the injection of adrenocorticopropic hormone (5 IU porcine-ACTH/day) or melanocyte-stimulating hormone (35 micrograms synthetic alpha-MSH/day) was ineffective. Additional pinealectomy influenced neither the inhibitory effects of hypophysectomy on coat pigmentation and body weight nor the stimulatory effects of prolactin substitution in hypophysectomized animals. Thus, the study provides evidence that the effects of the pineal gland on annual changes in body weight and coat color are mediated via the pituitary.     

The effect of hypophysectomy on chloride balance in young-of-the-year bowfin, Amia calva

The effect of hypophysectomy on chloride balance was examined in young-of-the-year bowfin, Amia calva. Hypophysectomy resulted in decreased serum and total body chloride levels but not in serum and total body sodium levels. Hypophysectomy resulted in decreased chloride influx with no effect on chloride efflux or sodium fluxes. Prolactin therapy reversed the effect of hypophysectomy on electrolyte balance but caused a significant reduction in serum protein.     

The role of the hypophysis and the hypophyseal hormone prolactin in maintenance of the sexual specificity of the metabolism of testosterone and 5-alpha-dihydrotestosterone in rat liver slices]

Hypophysectomy of rats 55 days after birth causes profound changes in the sexually differentiated liver metabolism of testosterone and 5alpha-dihydrotestosterone, which were studied when the rats were 80 days old. 1. Metabolism of testosterone after hypophysectomy: The turnover of testosterone decreased significantly to the same level in both sexes. The effect was especially marked in the female, which normally has a high turnover of this compound. The sexual differences in the patterns of metabolites were also lost, owing to the following changes: In the male, the high level of metabolites of the 3beta-hydroxy-5alpha-androstane type falls to the low level found in the female controls. The low level of 4-androstene-3,17-dione in the female increases to the high level found in the male controls. The concentrations of testosterone increase and those of the metabolites of the 3-oxo- and 3alpha-hydroxy-5alpha-androstane decrease to values that are significantly much higher or lower, respectively, than the normal values found in the control animals. 2. Metabolism of 5alpha-dihydrotestosterone after hypophysectomy: In comparison with the controls, the turnover of this substrate is significantly decreased by the same factor in both sexes; thus the difference between the sexes persists. In the pattern of metabolites, the sexual differences are still apparent, but less marked. The levels of metabolites show two opposing changes: a significant increase in the concentration of 3beta-hydroxy metabolites, and a significant decrease in the concentration of 3alpha-hydroxy metabolites; although the activity of the microsomal 3alpha-hydroxysteroid dehydrogenase increases by a factor of 3 - 4 in both sexes after hypophysectomy[1]. This discrepancy indicates a compartmentalization of androgen metabolism in the liver cell, in which delta4-5alpha- and 3beta-hydrogenation occur on the membranes of the endoplasmic reticulum, whereas 3alpha-hydrogenation occurs in the cytosol. 3. Action of prolactin on the metabolism of testosterone in hypophysectomized animals: Prolactin (125 mug twice daily from the 70th to the 79th day of life) causes a significant acceleration of the delta4-5alpha-hydrogenation, which is recognized as a significant increase in the concentrations of 5alpha-androstane metabolites; the 3beta-hydroxy compounds in both sexes reach the normal level of male control animals. The significant increase in the concentration of 3alpha-hydroxy compounds is accompanied by a partial reestablishment of the sexual differences. The sex differences in androgen turnover and metabolite pattern are subject to a hypophyseal regulation, which is separate from the gonadotropic partial function. The hydroxylation activity of the liver, measured as the production of C19O3-steroids, is not significantly affected by hypophysectomy or by treatment with prolactin.     

Changes in osmotic water permeability of the eel gills during seawater and freshwater adaptation

Summary Changes in osmotic water permeability of the isolated gills of the Japanese eel,Anguilla japonica were studied during transfer to seawater or to fresh water. The water permeability increased gradually during the course of seawater transfer and attained a maximal level after 2 weeks. The water permeability of the freshwater eel gills was reduced when calcium ions were added to the incubation medium at a concentration of 1 mM, where-as no effect of the ion was observed on the gills of the seawater-adapted eel even at a higher concentration (10 mM). In contrast to seawater transfer, the water permeability decreased to a low level almost immediately (3 h) after transfer from seawater to fresh water. The acute reduction of the water permeability was also seen in the gills of the hypophysectomized eel after transfer to fresh water.The gradual increase in the gill water permeability during seawater transfer is correlated with an increase in the number of chloride cells. In scanning electron microscopy, chloride cells of seawater-adapted eel gills exhibit a pit-like structure, which was larger than in the freshwater eel. On transfer from seawater to fresh water, the pit diameter became smaller within 6 h. Hypophysectomy did not affect the change in gill surface structures during transfer to fresh water. The junctions between the chloride cells of seawater eel gills are reported to be of the leaky type. The parallel change in osmotic water permeability and in pit size of the chloride cells during seawater or freshwater transfer or after hypophysectomy suggests that these cells could provide a major route of water as well as ion movement.This paper is a portion of a thesis presented to Hokkaido University by t. Ogasawara in partial fulfilment of the requirements for Doctor of Fisheries     

A New Proposal for the Action of Vasopressin, Based on Studies of a Complex Synthetic Membrane

The total osmotic flow of water across cell membranes generally exceeds diffusional flow measured with labeled water. The ratio of osmotic to diffusional flow has been widely used as a basis for the calculation of the radius of pores in the membrane, assuming Poiseuille flow of water through the pores. An important assumption underlying this calculation is that both osmotic and diffusional flow are rate-limited by the same barrier in the membrane. Studies employing a complex synthetic membrane show, however, that osmotic flow can be limited by one barrier (thin, dense barrier), and the rate of diffusion of isotopic water by a second (thick, porous) barrier in series with the first. Calculation of a pore radius is meaningless under these conditions, greatly overestimating the size of the pores determining osmotic flow. On the basis of these results, the estimation of pore radius in biological membranes is reassessed. It is proposed that vasopressin acts by greatly increasing the rate of diffusion of water across an outer barrier of the membrane, with little or no accompanying increase in pore size.     

Response of the hypothalamic neurosecretory system of the female catfish, Heteropneustes fossilis (Bloch), to hypophysectomy.

The effect of hypophysectomy on the hypothalamic neurosecretory system of the catfish, H. fossilis, was studied. Hypophysectomy resulted initially in an accumulation of NSM at the distal ends of the cut axons. The axons had grown and were reorganized into a neurohypophysis-like structure 3 weeks after hypophysectomy, and this persisted even more than 3 years post-hypophysectomy.     

Role of sex steroids and the pituitary in regulating the level of a specific estrogen-binding protein in rat liver

The effects of androgens (A), estrogens (E) and hypophysectomy on the content of an unusual rat liver estrogen-binding protein (UEBP) were studied by the differential quantitative method of the UEBP content measurement. The UEBP content was shown to increase during maturation of male rats. After A injections the UEBP content was high only in the liver of prepubertal but not of mature or immature males. Castration or hypophysectomy of mature males equally caused a decrease in the UEBP content in mature males whereas subsequent administration of A made it completely return to normal. Hypophysectomy of castrated males did not alter the UEBP content. A single injection of E provoked an appreciable reduction in the UEBP level after several days. Administration of A interfered with the inhibitory action of E after simultaneous injection of A and E and recovered the E-induced lowering of the UEBP content upon administration of A following E. Hypophysectomy of castrated males did not affect significantly the UEBP level. The UEBP content was insensitive to the direct action of pituitary factors. The pituitary is necessary for the realization of the effects of E alone but not A. It is suggested that the regulatory role of A consists in the maintenance of the constant optimal UEBP level in rat liver.     

Effect of adrenalectomy on distal tubule water permeability of the Brattleboro rat

The mechanism of impaired water excretion in adrenalectomized mammals is unclear. Previous workers have suggested that one cause might be increased water permeability of the distal nephron, allowing back diffusion of water from tubular fluid diluted by the ascending limb. Evidence to support this mechanism in previous studies has been confounded by simultaneous changes in steroid and antidiuretic hormone levels. We compared osmotic and diffusional water permeability of the surface late distal tubule in vivo in intact and adrenalectomized Brattleboro rats, which are free of antidiuretic hormone. The adrenalectomized rats were demonstrated to have impaired diluting capacity in clearance studies. Adrenalectomized rats had a sixfold increase in osmotic permeability and a 1.5-fold increase in diffusional permeability over intact controls. Adrenal steroids have a specific action on water permeability of the distal nephron, independent of antidiuretic hormone.     

Prolactin-releasing peptide is essential to maintain the prolactin level and osmotic balance in freshwater teleost fish

We administered prolactin-releasing peptide (PrRP) or anti-PrRP antiserum to goldfish in fresh water and analyzed their effects on prolactin and osmoregulatory mechanisms. The pituitary mRNA level of prolactin increased by PrRP but decreased by anti-PrRP. The rate of water inflow in the gills decreased by PrRP and increased by anti-PrRP, showing that PrRP restricts branchial water permeability, as also restricted by prolactin. PrRP also expanded the mucous cell layers on the scales, which may restrict efficiently water inflow by the mucous system. Eventually, the plasma osmotic pressure decreased by anti-PrRP. We conclude that PrRP is essential to maintain prolactin levels and osmotic balance in fresh water.     

Further characterization of the effects of hypophysectomy, FSH and estrogen on LH stimulation of testosterone production in Leydig cells isolated from immature rats.

Hypophysectomy of immature rats results after 5 days in a loss of LH responsiveness of Leydig cells. LH responsiveness can be partly maintained by treatment with FSH for 5 days. When estradiol benzoate was administered together with FSH to hypophysectomized rats the maintenance of LH responsiveness was not observed. The loss in LH responsiveness after hypophysectomy in terms of testosterone production could not be explained by either a change in the amount of Leydig cells present in the Leydig cell preparation or to a higher conversion of testosterone. The LH-stimulated cAMP production in cells from hypophysectomized rats was very low compared to cells from intact rats. There was no difference between cAMP production of Leydig cells from untreated, FSH-treated or FSH plus estradiol benzoate treated hypophysectomized rats. During the first 2 days after hypophysectomy LH responsiveness in both untreated and FSH-treated rats showed a comparable decrease. From day 2 after hypophysectomy LH responsiveness remained at a constant level in cells from rats treated with FSH, but declined further in cells from untreated rats. A single injection of estradiol benzoate to hypophysectomized rats treated with FSH counteracted the effect of FSH on LH responsiveness, but only when estradiol was administered at that time after hypophysectomy, when the effect of FSH on LH responsiveness was clear.     

Effects of prolactin and growth hormone on plasma levels of lysozyme and ceruloplasmin in rainbow trout

In vivo and in vitro effects of prolactin (PRL) and growth hormone (GH) on plasma levels of lysozyme and ceruloplasmin were examined in the rainbow trout (Oncorhynchus mykiss). Hypophysectomy had no effect on the plasma lysozyme level. Implantation of PRL- or GH-containing cholesterol pellets increased the lysozyme level in a dose-related manner. After hypophysectomy and sham operation, plasma ceruloplasmin was elevated above the level in intact fish, suggesting inflammation caused by the surgery. PRL or GH treatment significantly attenuated the increased level of ceruloplasmin in the operated fish. Expression of lysozyme mRNA was detected in the leucocytes isolated from the peripheral blood by RT-PCR. In vitro administration of PRL or GH showed no effect on the proliferation of isolated leucocytes or on the total protein content; however, lysozyme activity in the medium increased in a dose-related manner. These results suggest that PRL and GH directly stimulate lysozyme production without affecting the proliferation of leucocytes, and the attenuated ceruloplasmin level increased in response to inflammation.     

Effect of hypophysectomy on plasma electrolytes and adrenal mineralocorticoid secretion in the terrestrial chelonian Testudo hermanni

Na, K, ACTH, corticosterone and aldosterone plasma levels were studied in Testudo hermanni after hypophysectomy and dexamethasone administration. Hypophysectomy as well as dexamethasone treatment caused a deep decrease in the plasma levels of electrolytes, corticosterone and aldosterone when compared to sham-operated or normal controls. ACTH plasma level was markedly lower in hypophysectomized or dexamethasone-treated tortoises when compared to the controls but never reached undetectable levels. Administration of ACTH significantly increased plasma electrolytes and hormone levels in hypophysectomized and dexamethasone-treated tortoises. The present data seem to indicate that the pituitary plays a significant role on electrolyte homeostasis and on the regulation of plasma mineralocorticoids level in terrestrial chelonians.     

Decreased inflammatory responsiveness of hypophysectomized rats to heat is reversed by a corticotropin-releasing factor (CRF) antagonist

Hypophysectomy, but not adrenalectomy, decreased (relative to sham-operated controls) the swelling and Evans blue dye extravasation responses of the anesthetized rat's pawskin to thermal injury. alpha-Helical CRF (9-41), a synthetic competitive antagonist of corticotropin-releasing factor (CRF) on isolated pituitary cells, did not affect in sham-operated rats the swelling response after immersion of the paw in 58 degrees C water for 30 s. Swelling was measured over a 1 h period using the fluid displacement method for quantifying paw volume. But, when alpha-helical CRF (9-41) was injected 92 micrograms/kg i.v. 10 min before or immediately after heat exposure, it both attenuated and reversed the insensitive state produced by hypophysectomy: that is, the swelling response reappeared. Under the same test conditions, naloxone hydrochloride, an opioid antagonist, was ineffective. The results suggest that hypophysectomy may induce a condition whereby endogenous CRF or CRF-like peptides may act as an anti-inflammatory agent.     

Diffusional water permeability of human erythrocytes and their ghosts

The diffusional water permeability of human red cells and ghosts was determined by measuring the rate of tracer efflux by means of an improved version of the continuous flow tube method, having a time resolution of 2-3 ms. At 25 degrees C, the permeability was 2.4 x 10(3) and 2.9 x 10(3) cm s-1 for red cells and ghosts, respectively. Permeability was affected by neither a change in pH from 5.5 to 9.5, nor by osmolality up to 3.3 osmol. Manganous ions at an extracellular concentration of 19 mM did not change diffusional water permeability, as recently suggested by NMR measurements. A "ground" permeability of 1 x 10(3) cm s-1 was obtained by inhibition with 1 mM of either p- chloromercuribenzoate (PCMB) or p-chloromercuribenzene sulfonate (PCMBS). Inhibition increased temperature dependence of water permeability for red cells and ghosts from 21 to 30 kJ mol-1 to 60 kJ mol-1. Although diffusional water permeability is about one order of magnitude lower than osmotic permeability, inhibition with PCMB and PCMBS, temperature dependence both before and after inhibition, and independence of osmolality showed that diffusional water permeability has qualitative features similar to those reported for osmotic permeability, which indicates that the same properties of the membrane determine both types of transport. It is suggested that the PCMB(S)- sensitive permeability above the ground permeability takes place through the intermediate phase between integral membrane proteins and their surrounding lipids.     

Effects of hypophysectomy on plastocyst survival, progesterone secretion and nidation in the spotted skunk.

12 female skunks were hypophysectomized during the 7-month preimplantation period. Sham operations were performed on 7 skunks by drilling through the basisphenoid but without exposing the pituitary. 22 skunks remained as controls. Complete hypophysectomy significantly reduced peripheral plasma progesterone levels within 40 days while there was a tendency for values to increase in sham hypophysectomized skunks. The only obvious effect hypophysectomy had on ovarian histology during the preimplantation period was the abolition of all antral follicles; corpora lutea remained unchanged for up to 90 days. Blastocysts from hypophysectomized skunks were undergoing a slow attrition of cells after Day 34, and there was some indication that hypophysectomy may have a deleterious effect as early as Day 22. Hypophysectomy significantly prolonged the preimplantation period in 6 out of 7 skunks. It was concluded that the pituitary is essential for initiation of nidation.     

Early changes of water diffusional transfer in maize roots under the influence of water stress

The time dependent response of the hydrodynamic root system to PEG-induced water stress was studied in intact maize Zea mays L. seedlings at intervals varying from several seconds to 3 h by detecting diffusional water transfer with the use of pulsed NMR. In order to establish the contribution of water transfer through aquaporins in response to water stress, the transmembrane water transport in control roots and roots treated with aquaporin blocker was detected. Changes in diffusional water transfer under stress were shown to depend on the duration of osmotic treatment, and include the series of heterogeneous processes. A transient pulsed jump in diffusional water transfer detected several seconds after beginning the osmotic treatment is associated with the spread of the wave of hydraulic pressure along the root. It is proposed that early responses of the hydrodynamic system of maize roots to PEG-induced water stress lies in the unequal change in water permeability of the plasmalemma and tonoplast resulting from the changes in aquaporin activity and perhaps in the escalation of water transfer along the cell vacuome.     

Hormonal regulation of lh stimulation of testosterone production in isolated leydig cells of immature rats: The effect of hypophysectomy,fsh, and estradiol-17β

Testosterone production in isolated Leydig cells from testes of immature and adult rats was stimulated by addition of LH in a dose dependent way. Hypophysectomy of adult rats had no influence on LH-stimulated testosterone production in isolated Leydig cells after 5 days. In contrast hypophysectomy of immature rats resulted after 5 days in an almost complete loss of LH sensitivity of isolated Leydig cells. Daily administration of FSH during 5 days starting immediately after hypophysectomy maintained LH responsiveness of isolated Leydig cells of immature rats. Also FSH administration starting on day 5 after hypophysectomy resulted in a restoration of LH responsiveness. Estradiol benzoate, injected simultaneously with FSH, abolished the FSH-induced LH responsiveness.     

The ontogeny of immunoreactive beta-endorphin and beta-lipotropin in the rat ovary

We have investigated the ontogeny of, and the effect of hypophysectomy on, immunoreactive beta-endorphin in rat ovaries. Total levels rose with ovarian weight from nondetectable levels at 5 days of age to approximately 0.15 pmol/ovary at 80 days; thereafter, the levels remained constant through 201 days of age. Hypophysectomy decreased both ovarian weight and the total content of immunoreactive beta-endorphin, but the concentration per weight was not significantly altered. Most of the immunoreactive beta-endorphin before puberty chromatographed like authentic beta-endorphin, but after puberty most chromatographed like beta-lipotropin. Hypophysectomy did not alter this chromatographic pattern.