Experimental techniques for screening of antiosteoporotic activity in postmenopausal osteoporosis

Postmenopausal osteoporosis, a silent epidemic, has become a major health hazard, afflicting about 50% of postmenopausal women worldwide and is thought to be a disease with one of the highest incidences in senile people. It is a chronic, progressive condition associated with micro-architectural deterioration of bone tissue that results in low bone mass, decreased bone strength that predisposes to an increased risk of fracture. Women are more likely to develop osteoporosis than men due to reduction in estrogen during menopause which leads to decline in bone formation and increase in bone resorption activity. Estrogen is able to suppress the production of proinflammatory cytokines like interleukin (IL)-1, IL-6, IL-7 and tumor necrosis factor (TNF-α). This is why these cytokines are elevated in postmenopausal women. In this review article we have made an attempt to collate the various methods and parameters most frequently used for screening of antiosteoporotic activity in postmenopausal osteoporosis. Pertaining to ovariectomized animal model, this is the most appropriate model for studying the efficacy of different drugs to prevent bone loss in postmenopausal osteoporosis.

Influence of Simvastatin-Loaded Implants on Osseointegration in an Ovariectomized Animal Model

The success of bone implants in the presence of osteoporosis is limited by lack of osseointegration between the implant and the natural bone. This study applied an electrochemical process to deposit simvastatin-nanohydroxyapatite (HA) coatings on porous implant surfaces and investigated the effects of these simvastatin-HA coatings on implant surfaces in an animal model of osteoporosis. In this study, simvastatin-HA coated implants were inserted into the tibia of osteoporotic rats. After 2, 4, and 12 weeks, tissue was retrieved for histomorphometric evaluation. The results indicated that the simvastatin-HA coatings increased bone-implant contact and new bone formation around implant surfaces. In conclusion, implants loaded with simvastatin by an electrochemical process improved implant osseointegration in osteoporotic rats. Furthermore, the increased concentration of simvastatin could affect the osseointegration, but the dose-effects also need further investigation.

THE EFFECTS OF OVARIAN STEROIDS ON FOOD AND WATER INTAKE AND BODY WEIGHT IN THE FEMALE RAT

ABSTRACT The influence of ovarian steroids on food intake (FI), water intake (WI) and body weight (BWt) was measured under various conditions. Ovariectomy results in an increase in FI and BWt, which plateaued around one month after surgery. Daily injection of 1.5 μg oestradiol benzoate (OB) initiated at this time significantly reduced both FI and BWt. This effect of daily OB treatment on FI is only transitory since the FI returns to normal during OB treatment although the effect on BWt is maintained throughout and beyond OB treatment. Following ovariectomy, WI gradually falls, but is returned to normal by daily OB treatment. When oestrogen treatment is initiated at the time of ovariectomy, the increase in FI and BWt is prevented. In additional ovariectomized rats, 3 μg OB was injected every fifth day with either progesterone or oil administered on the intervening days. Although no influence of progesterone injection (either with OB or alone) was detected, the intermittent injection of OB induced cyclic suppression of FI, and the pattern of FI approached that of the intact cycling female. Adaptation to the intermittent injection of OB was not observed. Finally, OB treatment was found to decrease the increased FI seen during pseudopregnancy by a proportion similar to the effect of oestrogen in the long-term ovariectomized animal. These results suggest that oestrogen, but not progesterone, is the ovarian hormone active in the regulation of intake parameters and body weight in the female rat.

THE BIOGENESIS OF PRIMARY SEX HORMONES

1. A method is given for the extraction and fractionation of rabbit urines which frees these urines of inactive chromogens but permits a quantitative recovery of estrone and estriol for the colorimetric determination of these compounds. 2. Estrone and estriol content of rabbit urine extracts can be determined by the concentration of the colored compound they form upon diazotization with sulfanilic acid and by the modified phenolsulfonic acid test of Cohen and Marrian. Estriol can be determined by the specific reaction first described by David. The technique for these tests is presented. 3. Estriol (300 micrograms) injected into rabbits (a) in heat, (b) pregnant, (c) pseudopregnant, (d) hysterectomized in heat, (e) hysterectomized pseudopregnant, (f) ovariectomized, is excreted in the urine as estriol. Rabbit does in the luteal phase (b, c, and e) excrete 3 to 4 times the amount of estriol excreted by females without corpora lutea (a, d, and f). 4. When estrone (300 micrograms) is injected into the same types of rabbit does types a, b, and c excrete both estrone and estriol, type f excretes both estrone and estriol shortly after ovariectomy, but only estrone at 2 months after castration. Hysterectomized animals (types d and e) never excrete estriol after estrone injection. The total urinary estrin (estrone plus estriol) in estrone-injected animals is increased 2 to 3 times in animals in the luteal phase (b, c, and e). 5. It is concluded that the uterus is the site of conversion of estrone to estriol, and that the conversion cannot take place in a uterus completely free of ovarian control (e.g., in long time ovariectomized animals). 6. In neither estrone-injected nor estriol-injected females is all the injected hormone recovered in the urine. The maximum recovery is 66 per cent. When estrone-benzoate (600 micrograms) is injected 94–98 per cent of the hormone is recovered from animals in the luteal phase (types c and e) and about 79 per cent in an ovariectomized female (type f). These data are taken to indicate that luteal secretions give partial protection against destruction to the hormones. 7. The observation that in certain of the urine extracts the hormone titer by bioassay is somewhat higher than the colorimetric titer may indicate that there is a slight conversion of estrone to estradiol, particularly since no equilenin was found in any of the extracts by colorimetric test. 8. The simultaneous injection of 300 micrograms of estrone and 500 micrograms of progesterone 4 days after an initial injection of 300 micrograms of estrone results in: (1) an increased estrin excretion in females in heat, hysterectomized unmated, and ovariectomized, and a slight decrease in the pseudopregnant female; (2) the appearance of estriol in the urine of the long time ovariectomized animal with no urinary estriol in a control ovariectomized animal receiving no progesterone. These findings are taken to prove that the conversion of estrone to estriol occurs in the uterus under the influence of progesterone. Since animals in heat produce small amounts of estriol after estrone injection it is inferred that the ovaries of estrus rabbits produce small amounts of corpus luteum hormone in the absence of formed corpora lutea.

Studies on the hypophysectomized ferret, VI. ─Comparison of the response to œstrin of anœstrous, ovariectomized and hypophysectomized ferrets

Most of the work dealing with the relation between tire anterior pituitary body and the reproductive organs has tended to show that changes in the accessory reproductive organs in hyper- or hypo-pituitarism are merely secondary to changes in the gonads. If this is so, the atrophy of the vagina and uterus after hypophysectomy should be no greater than after ovariectomy, and the sensitivity to œstrin in the two conditions should be similar. On the other hand, certain work has suggested that the substances secreted by the anterior lobe may have some direct effect on the accessory organs, so that the uterus and vagina of the hypophysectomized animal might be less sensitive to œstrin than those of the ovariectomized animal, especially if the administration of œstrin has any stimulating action on the anterior lobe. Accordingly, Smith (1932) investigated the comparative sensitivity of the two types in the rat, and was unable to demonstrate any essential difference. We have been led to consider the same problem in hypophysectomized ferrets from the point of view of sensitizing the uterus to the action of the corpus luteum hormone. We have injected with œstrin three types of ferret, anœstrous, ovariectomized anœstrous and hypophysectomized anœstrous, in all of which the appearance of the accessory organs is similar (IV, p. 530).