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Basic somatomedin (B-SM) receptors in human term placenta explants.
Biochemical and Biophysical Research Communications
|July 31, 1984
Summary
Basic somatomedin (B-SM) binds to human placenta explants and stimulates nutrient uptake, suggesting an endocrine role. Placental cells do not produce B-SM, indicating it acts from outside the tissue.
Area of Science:
- Endocrinology
- Reproductive Biology
- Cell Biology
Background:
- Basic somatomedin (B-SM) is a growth factor with potential roles in placental function.
- Understanding B-SM's interaction with the human placenta is crucial for comprehending fetal development and maternal-fetal exchange.
Purpose of the Study:
- To investigate the binding characteristics of B-SM to human placental explants.
- To determine the effect of B-SM on nutrient transport, specifically alpha-aminoisobutyrate (AIB) uptake, in placental tissue.
- To elucidate the source and action (endocrine vs. paracrine) of B-SM on the human placenta.
Main Methods:
- Cultured term human placental explants were used to study B-SM binding.
- Specific binding assays and affinity cross-linking with [125I]B-SM were performed.
- The effect of B-SM on AIB uptake was measured in a dose-dependent manner.
- Hormone degradation and SM activity in incubation media were assessed.
Main Results:
- B-SM exhibited specific binding to human placental explants, with weak inhibition by insulin.
- Affinity cross-linking identified a B-SM binding subunit of Mr 140 K.
- B-SM significantly stimulated placental AIB uptake in a dose-dependent manner.
- Placental explants did not produce measurable B-SM, and SM activity decreased in incubated media.
Conclusions:
- Human placental explants possess specific binding sites for B-SM.
- B-SM directly influences placental nutrient transport, enhancing AIB uptake.
- The findings support an endocrine action of B-SM on the human placenta, rather than a local paracrine effect.