Lactation in the Rabbit: Mammary Blood Flow and Cardiac Output

Abstract

In anaesthetized rabbits, cardiac output (c.o.) and its distribution to the mammary glands, heart, liver and kidneys have been determined in established lactation (11)(12)(13) days), late lactation (26-27 days) and in virgins. During lactation, the volume of circulating blood, c.o., mammary blood flow and mammary weight were significantly greater than in virgins. There were no significant differences in c.o. and % c.o. received by the mammary glands between established and late lactation, and no significant decrease in mammary blood flow in late lactation. The weights of the liver and kidneys were significantly increased in lactation but there were no significant differences in liver, heart (coronary) and kidney blood flow. The rate of growth of the young was positively and significantly correlated with % c.o. received by the mammary glands and mammary weight, but not with c.o. Strong correlation was also observed between the % c.o.received by the mammary glands and mammary weight.There were no significant differences in c.o., mammary % c.o. and mammary blood flow in animals in established lactation 2-3 h and 24 h after suckling (i.e. shortly after and just before suckling). By 48 h after the last suckling mammary blood flow and % c.o., but not c.o., were significantly decreased. Possible factors causing these changes are discussed.The results are discussed in relation to the change in milk composition that occurs in late lactation in this species and to the role and effects of prolactin. It is suggested that events occurring during lactation have different sensitivities to prolactin.The cardiovascular system is profoundly altered during lactation. For example, apart from an increase in blood flow to the mammary glands, cardiac output (c.o.) is higher in lactating rats than in non-lactating females [Chatwin, Linzell and Setchell, 1969; Hanwell and Linzell, 1973a, b]. Similarly, c.o. is high in latepregnant and lactating goats [see Linzell, 1974;Hanwell and Peaker, 1977].In the rabbit, a marked change in milk composition occurs following peak lactation. The concentrations of lactose and potassium fall while those of sodium, chloride, protein and fat rise [Gachev, 1963a[Gachev, , 1971bCowie, 1969;Linzell and Peaker, 1971;Peaker and Taylor, 1975], even though milk yield remains relatively high. Since the administration of prolactin will reverse or tReprint requests to M.P.

NADH Fluorescence Imaging of Isolated Biventricular Working Rabbit Hearts

“…It is important that the perfusate solution provide enough oxygen and metabolic substrate to support biventricular heart function. Standard crystalloid buffer solutions, such as Krebs-Henseleit 16,17,25 or Tyrodes 26,27 , have oxygen solubilities as high as 5.6 mg/L. When these solutions are gassed with carbogen (a gas blend of 95% O 2 and 5% CO 2 ) and contain suitable metabolic substrate (glucose, dextrose, and/or sodium pyruvate), they are appropriate for biventricular working hearts beating at normal sinus rates (approximately 180 bpm for a rabbit).…”

Knowledge Gaps and Current Evidence Regarding Breastfeeding Issues in Mothers with Chronic Diseases

“…A study in rats exhibited significant increase in cardiac output in breastfed vs. non-breastfed animals [ 105 ]. Similarly, circulating blood volume and cardiac output were found increased during lactation in rabbits [ 106 ]. Lactating hormones, like prolactin and oxytocin, have been associated with aggravation of maternal cardiac diseases, including PPCM and aortic dissection in the context of Marfan syndrome [ 32 , 107 ].…”

NADH Fluorescence Imaging of Isolated Biventricular Working Rabbit Hearts

“…LV cardiac output can be determined by measuring the flow rate of perfusate exiting the aortic block (mL/min). Normal cardiac output is between 14.77 and 16.43 mL/min per 100 g of body weight 17 and averages 340 mL/min for a 2.2 kg rabbit. Aortic pressure should resemble the pressure signal shown in Figure 1.…”