Aliquots of infranatants from adipose tissue of wt and perilipin-null mice were tested for lipolytic activity as described under Materials and methods. Equivalent cellular aliquots were electrophoresed under SDS-PAGE, immunoblotted with affinity-purified anti-HSL, and scanned with a densitometer. The values for densitometric scans were divided by the activity values to give specific activities, revealing that the samples from both types of animals had identical specific activities.