− mice.

40S

Abstracts

P 33 DIETARY FRUCTOOLIGOSACCHARIDES INCREASE CALBINDIN-D9K LEVELS ONLY IN THE LARGE INTESTINE IN RATS INDEPENDENT OF DIETARY CALCIUM DEFICIENCY OR SERUM 1,25 DIHYDROXY VITAMIN D LEVELS Atsutane Ohta t, Kensuke Sakai *, Yasuko Motohashi *, Misao Takasaki t, Hiromi Inaba *, Keiko Sakuma* and Howard Morris ~ Bioscience Laboratories, Meiji Seika Kaisha, Ltd. "+Department of Molecular Nutrition, Kagawa Nutrition University ~iInstitute of Medical and Veterinary Science, Adelaide University Dietary short-chain fructooligosaccharides (Sc-FOS) increase mucosal calbindin-D9k (CaBP) levels in the large intestine whereas levels in the small intestine are decreased in rats. In the present stud3', we investigated the mechanism by which Sc-FOS reduce this increase in CaBP in the large intestine by measuring intestinal CaBP levels in rats fed normal and calcium-deficient diets. Dietary groups included a calcium-containing (0.5%) diet with or without Sc-FOS (100g/kg diet) mad a calcium-deficient (0.01%) diet with or without Sc-FOS (100g/kg diet). The rats were fed these diets for 10 days following which the}' were killed and the intestine removed for collection of the entire mucosa which was divided into four segments, i.e., proximal and distal segments of the small intestine, the cecum and the colo-rectum Mucosal CaBP and plasma Ca, 1,25(OH)zD3, 25(OH)D3, parathyroid hormone and calcitonin levels were measured. Feeding of calcium deficient diet resulted in an increase in CaBP levels in the small intestine, but did not influence levels in the large intestine. Moreover, a significant positive correlation between plasma 1,25(OH)2D3 and CaBP levels in the case of both small intestinal segments was observed, but not in the case of the large intestinal segments. Sc-FOS increased CaBP levels in the large intestine. These results suggest that the large intestinal CaBP levels do not change in response to dietary Ca conditions and are not regulated by circulating 1,25(OH)2D3 indicating that the effect of Sc-FOS on CaBP levels in the large intestine is independent of the action of 1,25(OH)2D3.

P 35 D I S P R O P O R T I O N A L S K E L E T A L G R O W T H AND M A R K E D L Y D E C R E A S E D B O N E M I N E R A L C O N T E N T IN G R O W T H H O R M O N E R E C E P T O R 4- MICE.

~'2SiOgrenK, ILindberg M, 5Coschigano KT, l'~I'6mell J, 4Mohan S, llsaksson OGP, 3Baumann G, SKopchick JJ, IOhlsson C IDept of Internal Medicine, RCEM, Sahlgrenska University Hospital, S-413 45 Goteborg, Sweden; 2Dept of Physiology, University of Goteborg, S-405 30 Goteborg, Sweden, SDept of Medicine, Northwestern University Medical School, Chicago IL, USA, 4Dept of Medicine, Lonva Linda University, Pettis Veterans Administration Medical Center, Loma Linda, CA, USA, 5Edison Biotech Inst, Dept of Biomedical Sciences, College of Osteopathic Medicine. Ohio University, Athens, OH 45701, USA. Growth hormone (GH) is important for longitudinal bone growth as well as for a normal bone metabolism in adults. The aim of the present study was to analyse the skeletal proportions and adult bone metabolism in mice with an inactivated growth hormone receptor (GHR) gene. The lengths of femur, tibia and crown-rump were, as expected, decreased in GHR -/- mice compared x~ith wild type (wt) mice. Unexpectedly, GHR -/- mice displayed disproportional skeletal growth reflected by decreased femur/crown-rump and femur/tibia ratios. GHR-/- mice demonstrated decreased width of the growth plates in the long bones and disturbed ossification of the proximal tibial epiphysis. Bones from GHR -/- and wt mice were analyzed using Dual X-Ray Absorptiomet D" (DXA) and Peripheral Quantitative Computeriz~l Tomography (pQCT) techniques The area bone maneral density (BMD) as well as the bone mineral content (BMC)/body weight were sigruficantly decreased in GHR -/- mice compared with wt truce (BMD total body 91%, spine 80%, femur 68%, tibia 71% and cranium 71% of wt mice) The decrease in bone mineral content in GHR 4- mice was not due to decreased trabecular vohin~tric bone mineral density but to a decreased cross sectional cortical bone area associated with a decreased radial bone growth Mechanical strength of the bones was measured using a Mechanical Tester. Three-point-bending at the mid-diaphyseal region of the fennur showed a significant decrease in the maximal load needed to break the femur in GHR-/- (-68%) compared to wt mice. In conclusion, GHR /- mace demonstrate disproportional skeletal growth, markedly decreased bone mineral content and also decreased mechanical strength of the bones.

Bone Vol. 27, No. 4, Supplement O c t o b e r 2000:1S 54S

P 34 REDUCED DIETARY PHOSPHATE IMPROVES CALCIUM BALANCE 1N THE OVARIECTOMIZED RAT SR Schulz, PD O'Loughlin, HA Morris, Division of Clinical Biochemistry, Institute of Medical and Veterinary Science, Adelaide 5000, Australia Oestradiol (E2) deficiency has varied effects in the body, including an alteration of overall calcium balance caused by increased bone resorption, decreased renal tubular calcium reabsorption and decreased intestinal calcium absorption. The ovariectomized (ovx) rat model fed a 0 2 % calcium, 0.3% phosphate diet demonstrates a negative calcium balance in which the major component is malabsorption of calcium (1). Dietary phosphate is a major regulator of serum 1,25 dihydroxyvitamin D (1,25D) levels. We now report the effect on calcium balance and calcium absorption of reduced dietary inorganic phosphate levels from 0 3 % to 0.2% phosphate in the ovx rat model. 70, 6 month old female Sprague Dawley rats consuming a 0.2% calcium, 0.2% phosphate diet were randomly allocated to either sham operation, ovariectomy or ovariectomy with E2 replacement. At 19 and 99 days post-operation calcium balance and its components were measured by a 6-day balance technique. Serum 1,25D and alkaline phosphatase (ALP) and urine deoxypyridinoline (Dpd) were also measured. Ovx rats on a 0.2% phosphate diet demonstrated a positive calcium balance (sham = 0.081(0.023); ovx - 0.077(0.022); ovx + E2 = 0 100(0.012) NS (mmol calcium/day)(SEM)). The major component of the positive calcium balance was increased calcium absorption. Serum 1,25D and ALP and urine DPD levels increased in the ovx rat above sham levels and were suppressed with E2 replacement In conclusion, a small reduction in dietary inorganic phosphate has markedly stimulated calcium absorption in both sham and ovx rats, directly relating to an improved calcium balance E2 replacement appears to have an overriding effect over dietary phosphate to improve calcium balance. E2 deficiency results in a negative calcium balance by increased bone resorption, decreased renal tubular reabsorption of calcium and decreased intestinal calcium absorption. (1) O'Loughlin PD, Morris HA. 1998 Oestrogen deficiency impairs intestinal calcium absorption in the r a t J Physiol (Lond) 5 1 1 : 3 1 3 - 2 2

P 36 EFFECT OF ZOLEDRONATE IN A RABBIT MODEL OF DISTRACTION OSTEOGENESIS. Smith EJ 1'2, Smith NC ~, Briody jr, Gardiner EM 2, Little DG ~. ~Orthopaedic Research Unit New Children's Hospital Westmead NSW 2145. Australia. 2Bone and Mineral Research Program, Garvan Institute O f Medical Research, Sydney, N S W 2010, Australia. We report the effects of single dose zoledronate (a parenteral bisphosphonate) in a rabbit model of distraction osteogenesis. Twelve immature New Zealand white rabbits had mid diaphyseal tibia• osteotomies distracted lcm (ten percent) over fourteen days. Six rabbits were randomly assigned to receive an infusion of 0. lmg/kg zoledronate (Novartis) pert-operatively, and six controls received a saline infusion. DXA scans were performed on both legs at two, four and six weeks post-operatively. At six weeks the mean bone mineral density (BMD) for the zoledronate group was increased by 67 percent in the regenerate and 53 percent in the proximal adjacent bone of the operated leg, compared with the controls (p<0.05). The mean bone mineral content (BMC) for the zoledronate group was increased by 105 percent for the regenerate and 68 percent for the proximal adjacent bone compared with the controls (p<0.05). We have previously found that the BMC (and not BMD) correlates significantly with peak load in four-point bending for this model (r:= 0.79). A single pert-operative dose of zoledronate has a marked effect on new bone formation in and around the regenerate in distraction osteogenesis. We plan to explore the molecular events underpinning these increases in the near future. Clinical trials of this promising intervention are also planned.