Developmental changes in the activity of lipoprotein lipase (clearing-factor lipase) in rat lung, cardiac muscle, skeletal muscle and brown adipose tissue.

The lipoprotein lipase activity of the lung, skeletal muscle, heart muscle and brown adipose tissue of the rat was studied during the period from late foetal to adult life. The enzyme activity in all four tissues emerged substantially during the first 24th after birth. Subsequently, heart and lung enzyme activity remained relatively constant per unit wet weight of tissue. The enzyme activity present in brown adipose tissue and skeletal muscle was elevated per unit weight of tissue during suckling compared with other periods of life. Delivery of near-term foetuses stimulated the emergence of enzyme activity in all four tissues with the same time course as that evoked by normal delivery. The significance of the presence of the enzyme in the tissues and the activity changes which occurred during development are discussed in relation to possible mechanisms of control.