Calcium uptake and release by isolated cortices and microsomes from the unfertilized egg of the sea urchin strongylocentrotus droebachiensis

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6500991

Oberdorf, J A

Two subcellular fractions of the sea urchin egg were studied for their potential role in regulating the transient rise in cytosolic calcium that accompanies fertilization. Isolated cortices from unfertilized sea urchin eggs sequester calcium in an ATP dependent manner when incubated in a medium containing free calcium levels characteristic of the resting cell. This ATP dependent calcium uptake activity, measured in the presence of 5mM Na Azide to prevent mitochondrial accumulation, was increased by oxalate, and was blocked by 150 ..mu..M quercetin and 50 ..mu..M vanadate. Cortices preloaded with /sup 45/Ca in the presence of ATP dramatically increased their rate of calcium efflux upon the addition of (1) the calcium ionophore A23187 (10 ..mu..M), (2) trifluoperazine (200 ..mu..M), (3) concentrations of free calcium that activated cortical granule exocytosis, and (4) the calcium mobilizing agent inositol trisphosphate (IP3). This pool of calcium is most likely sequestered in the portion of the egg's endoplasmic reticulum (ER) that remains associated with the cortical region during its isolation. They have developed a method for obtaining a high yield of purified microsomal vesicles from whole eggs. This preparation also demonstrates ATP dependent calcium sequestering activity which increases in the presence of oxalate and has similar sensitivities to calcium transport inhibitors, however the isolated microsomal vesicles did not show any detectable release of calcium when exposed to IP3. Procedures originally developed for purifying calsequestrin were used to partially purify a 58,000 MW protein from the egg's microsomal vesicles.

• Research Organization: Boston Univ., MA (USA)
• OSTI ID: 6500991
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ANIMALS
AQUATIC ORGANISMS
ATP
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCIUM 45
CALCIUM ISOTOPES
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
ECHINODERMS
EGGS
ENDOPLASMIC RETICULUM
EVEN-ODD NUCLEI
FERTILIZATION
INTERMEDIATE MASS NUCLEI
INVERTEBRATES
ISOTOPES
MICROSOMES
MOLECULAR WEIGHT
NUCLEI
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANOIDS
PROTEINS
PURIFICATION
RADIOISOTOPES
SEA URCHINS
UPTAKE