Intestinal uptake of carnitine is increased in the neonatal period (Gross and Savaiano, BBA, 1993;1170:265) when carnitine status is low. To evaluate whether carnitine deprivation, such as seen in neonates receiving parenteral nutrition (TPN), further affects intestinal carnitine transport, newborn piglets were administered TPN that was either carnitine-free (CARN -, n=6) or supplemented with 400 mg/l L-carnitine (CARN +, n=6) for the first 10-14 days of life. Age-matched sow-fed piglets (n=5) were used as controls. Five mg/kg body weight of L-carnitine labelled with 20 μCi 3H-L-carnitine and 1μCi 14C-Polyethylene glycol-4000 were introduced into an isolated segment of upper jejunum. Blood samples were taken from the portal (PV) and central venous (CV) circulations at 15,30,45,60,120,180 and 240 minutes for measurement of radioactivity. The animals were then sacrificed and samples of jejunal fluid, jejunal mucosa and liver were obtained. Results: PV levels of 3H-L-carnitine were higher in CARN-than CARN + animals(P<0.05). Those in sow-fed controls were intermediate. During the first hour after instillation, δ (PV-CV), an indicator of hepatic uptake, was greater in CARN- than CARN+ or sow-fed piglets (P<0.03) and proportional to PV levels (P<0.001). Mean (±SD) values for exogenous L-carnitine found in tissues (μmol/mg protein) are shown below. Values in a row not sharing a common letter are significantly different, P<0.05.
The findings suggest that carnitine deprivation up-regulates and intravenous L-carnitine supplementation down-regulates intestinal carnitine transport in the parenterally alimented piglet.Table
