Studies on the control of mucin production

The process of synthesizing a mucin molecule is discussed, primarily from the standpoint of glycoconjugate biosynthesis. The control of the activation steps in the making of nucleotide sugars is detailed, stressing the molecular mechanisms operating. These include: supply of glycolytic intermediates; the pyridine nucleotide redox potential; the energy state as expressed in nucleotide potential; and feedback modifiers. Next, the glycosyl transferases are discussed, as are suggestions of control at the first committment step and the subjects of specificity of donor and acceptor molecules and the associational state of the glycosyl transferases. The secondpart of the paper describes a model system in vivo. The paired cat submandibular glands are exposed and, in one, blood supply and salivary duct are cannulated and the parasympathetic and sympathetic nerve exposed. This preparation uses the contralateral gland as control and enables certain questions to be asked: 1. Does the cell produce incomplete mucins when the biosynthetic rate is high? 2. Does the energy state of the cell 'keep up with' the high rates of synthesis? 3. What is the extent of post-synthetic modifications? 4. What cell types are involved in mucin elicited by different chemical or electrical stimuli? 5. What is the time involved in synthesis and storage?