Table 1. The earliest day of significant increase observed for each enzyme activity compared to respective 1-day-old tissue during development.

	A-SMase	N-SMase	Ac-CDase	N-CDase	Al-CDase	SM synthase	CD synthase
Liver	42	42	7	7	7	180	21
Kidney	180	180	42	42	42	42	21
Brain	180	42	42	21	180	21	21

acidic and neutral sphingomyelinases: A-SMase & N-SMase; acidic, neutral, and alkaline ceramidases: Ac-CDase, N-CDase and Al-CDase.