Hypertrophic and hyperplastic changes in the alimentary canal of the lactating rat

Abstract

DURING lactation in the rat the alimentary canal shows an increase in weight and nitrogen content compared with that of unmated controls (Poo, Lew and Addis, 1939), or pregnant rats (Boyne, Chalmers and Cuthbertson, 1953; Souders and Morgan, 1957). Po0 et al. included with the alimentary canal the entire contents of the abdomen and pelvis except for the liver, kidneys and uterus, whereas Boyne et al. examined the cleaned and empty gut and Souders and Morgan studied only the small intestine. The determinations were made on the loth day of lactation by Po0 et al., on the 16th day by Boyne et al. and immediately after weaning by Souders and Morgan.We felt that the increase in nitrogen content of the alimentary canal during lactation was suilicient to justify a more detailed study, the results of which are presented in this paper. MATERIALS AND METHODSAnimals and diet. Adult virgin or lactating, prirniparous Hooded Lister female rats were used in these experiments. The food was '' Diet 86 ", compounded as cubes by the North-Eastern Agricultural Coop. Soc. Ltd, Aberdeen. It contained: wheat 50 per cent.; barley 25; white fish meal 7; meat and bone meal 6 ; dried brewers' yeast 5 ; dried grass meal 5 ; sodium chloride 1; and cod liver oil or equivalent stabdised vitamins A and D, 1 per cent. Analysis gave: dry matter 85.7 per cent.; protein 20.0; fat 3.8; soluble carbohydrate (by difference) 53.4; fibre 3.3; and ash 5.2 per cent.Food and water were freely available to dam and litter in all experiments. In some experiments the cubes were milled to facilitate the recording of food consumption. All the lactating rats ate an unrecorded amount of wood-wool litter.Usually the litters were reduced to 8 young per rat on the day of birth, but since the results were apparently not influenced by litter size we have included some early data obtained from rats with litter size greater than 8.Weight of ufimentury d. Lactating rats were killed with ether vapour at daily intervals from the first day postpartum up to the early post-weaning period, at which dates their average body weight was 280 g. They were eviscerated and the omentum, mesentery and fat were removed from the viscera. The length of the small intestine was recorded and Peyer's patch= were counted. The small inhtine was then divided into three equal lengths, which for the purposes of this paper were regarded as corresponding approximately to duodenum, jejunum and ileum; the stomach, caecum and colon were treated separately. The parts were cut open, washed in water, blotted and weighed. Twelve virgin female controls of average body weight 260 g. were treated similarly. In the final experiment the young of primiparous rats were killed on the day I. PA-BMX.--VOL 85 (1963) 179 Acta anat., 43,264. This J o u d , 81,251.

Evidence for a reciprocal relationship between lipogenesis and ketogenesis in hepatocytes from fed virgin and lactating rats

“…Addition of dihydroxyacetone (5mM), which was found by Harris (1975) (Panek etal., 1977) and female (Harris, 1975;Mapes, 1977) rats which have been meal-fed with a low-fat high-carbohydrate diet, but in the present experiments we did not wish to interfere with the normal dietary regime of the rats. It is well established that lactating rats have a higher food intake than virgin rats (Cole & Hart, 1938;Fell et al, 1963) and this may play a role in the increased rate of lipogenesis. As expected, oleate (1 mM) decreased both the rate of endogenous lipogenesis (Table 1; Mayes & Topping, 1974) and that in the presence of dihydroxyacetone.…”

Effect of the Energy Density of Non-purified Diets on Growth, Gestation and Lactation in Mice

“…Apparently mice ingested feed at full ingestive capacity in the first and second weeks of lactation, but this capacity increased in the second week. Fell et al [12] found that the alimentary canal of lactating primiparous rats increased progressively in weight, size and total nitrogen content up to weaning, after which there was a decline. Macroscopic hypertrophy of the alimentary canal, particularly of the small intestine and caecum, was remarkable.…”

Associations between basal metabolic rate and reproductive performance in C57BL/6J mice

“…One possible reason for this failure is that previous studies have tended to measure BMR in pre-reproductive animals. Lactating mice show considerable morphological plasticity during lactation relative to the situation when they are virgins, including expansion of their alimentary tracts and liver sizes (Fell et al, 1963;Kennedy et al, 1958) with associated modulations of their resting metabolic rates (Speakman and McQueenie, 1996). Previously pregnant mice have a greater body mass, attributed to protein accumulation, than nonparous mice (Holinka, 1980).…”