Milk Production In Rats Research Articles

Central δ/κ opioid receptor signaling pathways mediate chronic and/or acute suckling-induced LH suppression in rats during late lactation.

In mammals, secretion of tonic (pulsatile) gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) is often suppressed during lactation. Suppression of GnRH/LH pulses in lactating dams is assumed to be caused by suckling stimuli and a chronic negative energy balance due to milk production. The present study aimed to investigate whether the central enkephalin-δ opioid receptor (DOR) signaling mediated the suppression of LH secretion by acute suckling stimuli and/or chronic negative energy balance due to milk production in rats during late lactation when dams were under a heavy energy demand. On postpartum day 16, the number of Penk (enkephalin mRNA)-expressing cells in the arcuate nucleus was significantly higher in lactating rats than in non-lactating control rats. Pulsatile LH secretion was suppressed in rats with chronic suckling or acute 1-h suckling stimuli 6 h after pup removal on day 16 of lactation. Central DOR antagonism significantly increased the mean LH concentrations and the baseline of LH pulses in rats with chronic suckling but not with acute suckling stimuli on day 16 of lactation. Besides, central κ opioid receptor (KOR) antagonism increased the amplitude of LH pulses in rats with the acute suckling stimuli on day 16 of lactation. These results suggest that central DOR signaling mediates the suppression of LH secretion caused by a negative energy balance in rats receiving chronic suckling during late lactation. On the other hand, central KOR signaling likely mediates acute suckling stimuli-induced suppression of LH secretion in rats during late lactation.

Effect of Aqueous and Ethanolic Extracts of Pimpinella anisum L. Seeds on Milk Production in Rats

Pimpinella anisum L. (P. anisum) is used as a galactagogue in traditional medicine; hence, the effect of aqueous and ethanolic extracts of P. anisum seeds on milk production in rats was evaluated. The milk production was assessed by measuring the pups' weights during the suckling period. The intraperitoneal LD50 values of P. anisum aqueous and ethanolic extracts were 4.93 and 3.77 g/kg, respectively. The aqueous (1 g/kg) and ethanolic extracts (1 g/kg) increased the milk production significantly (p < 0.001), with about 68.1% and 81% more milk being produced, respectively, than in the control group. The pups gained weight during the study period with the aqueous (0.5 and 1 g/kg, p < 0.05) and ethanolic (0.5 and 1 g/kg, p < 0.01) extracts. Thus, P. anisum aqueous and ethanolic extracts can increase milk production in rats.

Lactogenic activity of rats stimulated by Gunnera perpensa L. (Gunneraceae) from South Africa.

Gunnera perpensa L. (Gunneraceae) is a medicinal plant used by Zulu traditional healers to stimulate milk production. The effect of an aqueous extract of the rhizome of the plant on milk production in rats was investigated. Female lactating rats that received oral doses of the extract of G.perpensa significantly (p<0.05) produced more milk than controls. The plant extract did not however, significantly influence the levels of prolactin, growth hormone, progesterone, cortisol, ALT, AST and albumin in the blood. The mammary glands of rats treated with the extract showed lobuloalveolar development. The extract (0.8 µg/ml) was also found to stimulate the contraction of the uterus and inhibit (23%) acetylcholinesterase activity. The cytotoxicity of the extract (LC₅₀) to two human cell lines (HEK293 and HepG2) was 279.43 µg/ml and 222.33µg/ml, respectively. It is inferred that the plant extract exerts its activity on milk production and secretion by stimulating lobuloalveolar cell development and the contraction of myoepithelial cells in the alveoli. It is concluded that Gunnera perpensa contains constituents with lactogenic activity that apparently contribute to its effectiveness in folk medicine.

Effect of Aqueous and Ethanolic Extracts of Nigella sativa Seeds on Milk Production in Rats

Nigella sativa L. is used as a galactagogue in traditional medicine. Hence, the effects of aqueous and ethanolic extracts of N. sativa seeds on milk production in rats were evaluated. The measurement of milk production was by measuring pup weight during suckling period. The intraperitoneal LD50 values of aqueous and ethanolic extracts of N. sativa were 4.23 and 4.9 g/kg, respectively. The aqueous (0.5 g/kg) and ethanolic extracts (1 g/kg) increased milk production significantly (p < 0.001), producing about 31.3% and 37.6% more milk than control, respectively. During the study period, the pups gained weight with the aqueous (0.5 g/kg, p < 0.01) and ethanolic extracts (1 g/kg, p < 0.05). It is concluded that aqueous and ethanolic extracts of N. sativa can stimulate milk production in rats.

Efeitos da exposição à fumaça do cigarro sobre a produção láctea e o crescimento de filhotes de ratas

OBJETIVOS: Analisar o efeito da exposição à fumaça do cigarro na gestação e lactação sobre a produção láctea de ratas, ganho ponderal e crescimento linear dos filhotes. MÉTODOS: Três grupos de ratas foram estudados na gestação e lactação: 15 ratas expostas à fumaça do cigarro mais fluxo de ar, 18 ratas manipuladas, isto é, expostas ao fluxo de ar comprimido e 18 ratas controle. Os filhotes foram medidos e pesados a cada 5 dias, do primeiro ao 15º dia. A produção láctea foi estimada pelos métodos de captação de leite em 1 hora e ganho ponderal dos filhotes. RESULTADOS: Os filhotes das ratas expostos à fumaça do cigarro apresentaram menor peso e comprimento ao nascer. Durante a lactação, os filhotes das ratas expostas à fumaça e das apenas manipuladas ganharam menos peso que o grupo controle. A produção láctea pelo método de captação de leite em 1 hora foi reduzida no grupo exposto à fumaça e, em menor proporção, nas ratas do grupo manipulado. Pelo método do ganho ponderal dos filhotes, a produção láctea reduziu-se igualmente nos grupos exposto à fumaça e manipulado, comparados ao grupo controle. CONCLUSÕES: A exposição à fumaça do cigarro comprometeu o peso e o comprimento ao nascer, mas, durante a lactação, também a manipulação comprometeu o ganho de peso dos filhotes. A manipulação e, mais acentuadamente, a exposição ao tabaco prejudicaram a produção de leite.

The effects of exposing rats to cigarette smoke on milk production and growth of offspring

To analyze the effects of exposure to cigarette smoke during gestation and lactation on the milk production of rats and on the weight gain and linear growth of their offspring. Three groups of female rats were studied during gestation and lactation: 15 rats were exposed to cigarette smoke and air flow, 18 rats were handled, i.e., exposed to compressed air flow, and 18 rats were used as controls. Newborn rats were measured and weighed every 5 days, from the first to the 15th day. Milk production was estimated by 1-hour milk extraction and weight gained by litters. The offspring of rats exposed to cigarette smoke weighed less and were shorter at birth. During lactation, the offspring of rats exposed to smoke and also of rats that had merely been handled gained less weight than the control group. Milk production gauged by the 1-hour extraction method was reduced in the group exposed to smoke and, to a lesser extent, also in the group that had been handled. Milk production estimated according to the pups' weight gain was reduced equally in the groups exposed to smoke and merely handled, when compared to the control group. Exposure to cigarette smoke compromised the birth weight and birth length, but during lactation, handling also compromised weight gain of offspring. Handling and, to a greater extent, exposure to tobacco, were prejudicial to milk production.

Influence of maternal dietary calcium levels on milk zinc, calcium and phosphorus contents and milk production in rats

The aim of this study was to analyze zinc (Zn), calcium (Ca) and phosphorus (P) contents in milk and the lactational performance in rats fed different Ca levels. Female Wistar rats were fed during pregnancy and lactation with experimental diets containing 20% protein and high (0.90%, HCa), normal (0.60%, NCa) or low (0.20%, LCa) Ca levels. Milk samples were collected after 15 days to determine the milk mineral composition. Pup weight was recorded from birth to weaning (litter size: 6–8 pups) to determine weight gain and calculate milk production. At delivery there were no significant differences in the body weight of the pups between the groups, but at day 15, the LCa group showed lower values than both NCa and HCa groups ( p < 0.05 ) . The weight gain of the LCa group was significantly lower than of the HCa and NCa groups, between delivery and day 5 ( p < 0.05 ) . This reduced rate of weight gain led to the LCa group reaching weaning weight later than the other groups. Milk production (g/pup/day) was significantly lower when dams were fed the LCa than the NCa and HCa diets ( p < 0.05 ) . There were no significant differences among the groups in milk Ca, P and Zn levels and Ca/P ratio. The body mineral composition of the pups at birth did not differ between the groups; at weaning, however, both LCa and HCa groups had lower element contents than the NCa group ( p < 0.05 ) . In conclusion, dams fed with a diet containing low Ca levels produced smaller volumes of milk and their pups reached weaning weights later than the other groups. As the milk mineral composition was not affected, it can be hypothesized that in dams fed low dietary Ca, the smaller milk yield might have been a way of maintaining milk quality. High Ca levels affected neither pregnancy outcome nor lactational performance.

Effect of aqueous extract of Acacia nilotica ssp adansonii on milk production and prolactin release in the rat.

In view of the traditional belief that Acacia nilotica ssp adansonii (AN) can stimulate milk production in lactating women, experiments were performed to determine the effect of an aqueous extract of AN on milk production in rats. Female rats that received oral doses of aqueous extract of this plant during their first lactation produced about 59% more milk than controls (P<0.01). Pup weight gain was also significantly higher than that in the control group. A lower dose, comparable to that used by women to improve their milk yield, led to about 33% more milk with the same growth rate for pups as that in the high-dose group. The extract of AN was found to stimulate the synthesis and release of prolactin (PRL) significantly (P<0.05). In addition, the mammary glands of oestrogen-primed rats treated with the extract showed clear lobuloalveolar development with milk secretion. This study demonstrates that the aqueous extract of AN can stimulate milk production and PRL release in the female rat and could consequently have the properties claimed for lactating women.

Effects of active immunization against somatostatin or somatostatin analogues on milk production in rats

Effects of active immunization against various forms of somatostatin on milk production were investigated in rats. Somatostatin-14, somatostatin-28, or three different somatostatin analogues were conjugated to bovine serum albumin for immunogen preparation. Seventy female Sprague-Dawley rats were divided into seven groups and immunized against phosphate buffer (control 1), bovine serum albumin (control 2), somatostatin-14, somatostatin-28, or one of the somatostatin analogues (Octreotide, Tyr3-octreotide, and MK 608) at five weeks of age. Booster immunizations were performed at 7, 9, 12 weeks of age. Only somatostatin-14 injection induced the production of anti-somatostatin antibodies. There were no differences in blood GH and IGF-I concentrations and growth performance between somatostatin-14 group (with anti-somatostatin antibodies) and other groups (without the antibodies). In addition, mammary DNA, RNA, and protein contents, and the ratio of RNA to DNA and protein to DNA of somatostatin-14 group were not different from those of the other groups. Although rats immunized against somatostatin-14 showed the highest milk production among all groups, there was no statistical significance.

Ethanol Intake During Lactation Impairs Milk Production in Rats and Affects Growth and Metabolism of Suckling Pups

TAVARES DO CARMO, M. G., C. M. OLLER DO NASCIMENTO, A. MARTIN AND E. HERRERA. Ethanol intake during lactation impairs milk production in rats and affects growth and metabolism of suckling pups. ALCOHOL 18(1) 73–78, 1999.—From parturition, lactating Wistar rats were given 20% alcohol in drinking water and fed a solid diet ad lib (group AL). Pair-fed (PF) and control (C) rats were fed solid diet and given water ad lib (C). All animals were sacrificed on the 12th day of lactation. Ethanol treatment decreased food intake and milk production in lactating rats to a greater level than in PF rats, and a greater reduction in body weight of the AL pups was noted. Brain weight, protein concentration, and DNA content were also lower in pups of AL dams than of PF dams, whereas liver glycogen concentration was higher in the former. Pups from AL dams had higher circulating levels of β-OH-butyrate, triglyceride, and free fatty acids than those from either C or PF dams. Plasma glucose concentration was lower in both PF and AL than in C pups, whereas the AL group had lower plasma protein concentration than any of the other groups. We conclude that maternal alcohol intake during lactation greatly impairs milk production, and although the known increase of lipid content in milk in rats studied under similar conditions allows an enhanced lipidic components in the pups, this adaptation does not allow normal growth and brain development.

Maternal protein reserves and their influence on lactational performance in rats 3. The effects of dietary protein restriction and stage of lactation on milk composition

The effects of severe protein restriction following parturition on the changes in rat milk composition during lactation were investigated using multiparous female Sprague-Dawley rats caged individually following mating and offered a high-protein diet (H; 215 g crude protein (N x 6.25; CP)/kg dry matter (DM)) ad lib. until parturition. Following parturition, half the females continued to receive diet H, whilst the remainder were offered a diet low in protein (L; 90 g CP/kg DM) ad lib. On days 2, 4, 8 and 12 of lactation groups of females from both dietary treatments were used to provide a milk sample. Milk samples were analysed for their lactose (enzymically), protein (binding to Coomassie blue), lipid (gravimetrically) and mineral (spectrophotometrically) contents. The milk lactose concentration of group H increased with stage of lactation (r2 0.85, P < 0.001). Such an increase was prevented by diet L, and from day 8 of lactation the milk lactose of group L was lower (P < 0.05) than in group H. Group H milk protein concentration did not change during lactation and averaged 90.7 mg/g. Dietary protein restriction reduced the milk protein concentration of group L so that on days 2, 4 and 12 of lactation it was lower (P < 0.05) than that of group H. On day 8 of lactation the milk protein concentration of group L had increased (P < 0.05) and was comparable with that of group H. For group H, milk lipid averaged 166.8 mg/g and was generally unchanged during lactation. Diet L increased (P < 0.01) the milk lipid concentration (205.5 mg/g) compared with diet H and this was also significant on days 4 and 8 of lactation (P < 0.05). Group L milk lipid concentration also increased between days 4 and 8 of lactation (P < 0.05). Milk Na concentration declined during lactation in both dietary groups (P < 0.01) but was unaffected by dietary treatment. Both milk Ca and P concentrations increased (P < 0.01) during lactation in both dietary groups, whilst protein restriction also increased the Ca and P concentrations (P < 0.05). Milk K and Mg concentrations were unaffected by dietary treatment or stage of lactation. This significant alteration in the milk composition of severely protein-restricted dams, while possibly favouring the disposal of greater quantities of energy-yielding nutrients, suggests that equations developed for the estimation of milk production in rats cannot be used under such conditions.