The effects of birth weight on basal cardiovascular function in pigs at 3 months of age

Abstract

In man, epidemiological studies have shown that low birth weight (BW) is associated with an increased risk of cardiovascular disease in later life. In this study, the long-term consequences of variations in natural BW on basal cardiovascular function were investigated in pigs at 3 months of postnatal age. Low (< 1.41 kg; n = 20) and high (> 1.52 kg; n = 20) BW Large White piglets were selected from a total of 12 litters for study at 3 months of age. Basal mean arterial pressure (MAP) and heart rate (HR) were recorded for approximately 30 min using standard recording equipment and basal arterial blood samples were taken for hormone analyses. Concentrations of angiotensin-converting enzyme (ACE) were also measured in kidney, lung and plasma. Basal MAP, but not HR, in 3-month-old pigs was significantly inversely related to BW and positively related to the ratio of head length to BW. Postnatal growth rate of low BW pigs was slower than that of high BW pigs such that low BW piglets remained significantly smaller at 3 months of age. There were no differences in basal plasma adrenaline or cortisol concentrations between low and high BW pigs. However, basal plasma noradrenaline concentrations were significantly elevated in low BW compared to high BW pigs. Renal and pulmonary ACE levels were significantly reduced in low BW compared to high BW pigs. These data show that basal MAP in 3-month-old pigs is negatively associated with BW and positively correlated to disproportionate size at birth. This effect was associated with an increase in basal plasma noradrenaline concentrations.

Figure 1. Body weight at 3 months

The relationship between body weight at 3 months (m) of age (CW) and birth weight (BW) in pigs. CW = 3.3 + (17.6 × BW).

Figure 2. Basal mean arterial pressure (MAP) and heart rate (HR)

Basal MAP (A) and HR (B) in low and high BW pigs at 3 months of age. Numbers in parentheses represent the number of observations.

Figure 3. Basal mean arterial pressure (MAP) and heart rate (HR)

The relationships between MAP and birth weight (BW; A) and the head length:BW ratio (B). A, MAP = 120.5 - (13.8 × BW); B, MAP = 75.2 + (3.3 × head length:BW).

Figure 4. Basal catecholamine and cortisol concentrations

Basal adrenaline, noradrenaline and cortisol concentrations in low and high BW pigs at 3 months of age. Numbers in parentheses represent the number of observations. Low vs. high BW (unpaired t test): *P < 0.05.

Figure 5. Renal and pulmonary angiotensin-converting enzyme (ACE)

Renal (A) and pulmonary (B) ACE activity in low and high BW pigs at 3 months of age. Numbers in parentheses represent the number of observations. Low vs. high BW (unpaired t test): *P < 0.05.

Figure 6. Renal and pulmonary angiotensin-converting enzyme (ACE)

The relationships between renal ACE (A and B) and lung ACE (C and D) and the ratios of head length:birth weight (BW) and head length:current weight (CW). A, ACE = 8.9 - (0.7 × head length:BW); B, ACE = 6.8 - (3.4 × head length:CW); C, ACE = 7.1 - (0.4 × head length:BW); D, ACE = 5.4 - (1.6 × head length:CW).