ATP-dependent Ca2+ accumulation by microvesicles isolated from bovine neurohypophyses

Area of Science:

• Neuroendocrinology
• Cell Biology
• Biochemistry

Background:

• Microvesicles are membrane-bound vesicles involved in intercellular communication.
• The neurohypophysis is a key brain region for hormone release and regulation.

Purpose of the Study:

• To investigate the properties and potential function of microvesicles isolated from bovine neurohypophyses.
• To determine if these microvesicles are involved in calcium ion (Ca2+) transport and regulation.

Main Methods:

• Isolation of microvesicles from bovine neurohypophyses using ultracentrifugation.
• Assay of calcium accumulation in the presence of ATP and Mg2+.
• Investigation of the effects of oxalate and the Ca2+ ionophore A23187 on calcium uptake.
• Analysis of microvesicle protein composition using SDS-PAGE.
• Measurement of ATPase activity in the presence of Ca2+ and Mg2+.

Main Results:

• Isolated microvesicles demonstrated ATP- and Mg2+-dependent calcium accumulation.
• Oxalate stimulated, while the Ca2+ ionophore A23187 inhibited, calcium uptake.
• Microvesicles exhibited ATPase activity in the presence of Ca2+ and Mg2+.
• Protein composition analysis indicated that these microvesicles are distinct from neurosecretory granule membranes.

Conclusions:

• Bovine neurohypophyseal microvesicles possess calcium-accumulating and ATPase activities.
• Their distinct protein composition suggests they are not derived from retrieved neurosecretory granule membranes.
• These microvesicles may play a significant role in the regulation of intracellular calcium ion concentration within the neurohypophysis.