Exposure to a maternal low protein diet in utero programmes the rat foetus to develop hypertension (Langley & Jackson, 1994) and impaired renal function (Sahajpal & Ashton, 2003). Studies on senescent rats also revealed a long term reduction in bone area and bone mineral content, with a widening of the epiphyseal growth plate (Mehta et al., 2002), suggesting that skeletal growth may also be programmed in utero.The aim of this study was to determine the effects of a maternal low protein diet on renal calcium handling and bone morphology in young rats.Pregnant Wistar rats were fed isocalorific diets containing either 18% (normal, NP) or 9% (low, LP) protein from conception (Sahajpal & Ashton, 2003). After birth, all dams switched back to standard rat chow. Male offspring (NP n = 5-6 from n = 5 litters, LP n = 5-7 from n = 5 litters) were studied at 4 weeks of age. Renal clearance of ³H inulin and calcium was measured under Intraval anaesthesia (thiopentone sodium, 110 mg kg^-1,i.p.) in rats receiving euvolaemic fluid replacement of spontaneous urine output (Ahmed et al., 2003). Animals were humanely killed at the end of the experiment. Femurs were decalcified for histomorphometric assessments of matrix. Statistical comparisons were by unpaired t-test. Mean arterial blood pressure was higher (NP, n = 6, 82 ± 6 vs LP, n = 7, 111 ± 5 mmHg, P<0.01) and body weight was lower (NP 114.5 ± 3.6 vs LP 90.7 ± 5.2 g, P<0.01) in LP rats. Glomerular filtration rate (GFR) was lower, but calcium clearance (C_Ca) and both total (U_CaV) and fractional excretion (FE_Ca) of calcium were higher in LP rats (Table 1).