WBR0733
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Physiology |
| Sub Category | SubCategory::Endocrine |
| Prompt | [[Prompt::A researcher is studying the signaling pathways of hormones and their corresponding pathways in achieving their regulatory functions. Using mice, he activates liver fat-storing cells (FSCs) using phorbol myristate acetate to increase levels of platelet-derived growth factor (PDGF). In vitro experiments show that profiling of an enzyme activity is significantly increased following the increased production of PDGF. Which other endogenous compounds will most likely have the same signaling effect as PDGF?]] |
| Answer A | AnswerA::Insulin |
| Answer A Explanation | AnswerAExp::Insulin, like PDGF, uses the intrinsic tyrosine kinase activity to achieve its hormonal effects. |
| Answer B | AnswerB::Follicle-stimulating hormone (FSH) |
| Answer B Explanation | AnswerBExp::FSH uses the cAMP pathway to achieve its hormonal effect. |
| Answer C | AnswerC::Oxytocin |
| Answer C Explanation | AnswerCExp::Oxytocin uses the inositol triphosphate (IP3) signaling pathway to achieve its hormonal effects. |
| Answer D | AnswerD::Prolactin |
| Answer D Explanation | AnswerDExp::Prolactin uses a receptor-associated tyrosine kinase pathway to achieve its hormonal effect. |
| Answer E | AnswerE::Cortisol |
| Answer E Explanation | AnswerEExp::Cortisol utilizes a specific steroid receptor to achieve its hormonal effects. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Platelet-derived growth factor (PDGF) is a compound found in platelet alpha-granules and numerous cell types. It helps growth and proliferation of smooth muscle cells and fibroblasts. It has been hypothesized that PDGF's proliferative function may contribute to proliferative pathological processes, such as cancers and atherosclerosis. PDGF exerts its effects via an autocrine or paracrine fashion.
PDGF, similar to other growth factors and insulin, achieve their hormonal effects by the intrinsic tyrosine kinase signaling pathway. PDGF contains extracellular ligang-binding domains that are associated with intracellular domains. Following ligand binding, the receptor dimerizes; each subunit binding to one receptor molecule. Dimerization then causes activation of the enzyme protein kinase on the receptor via phosphorylation mechanisms. Educational Objective: Growth factors, such as PDGF, and insulin achieve their hormonal activity by the intrinsic tyrosine kinase signaling pathway. Reference: Heldin CH, Westermark B. Platelet-derived growth factor: mechanism of action and possible in vivo function. Cell Regulation. 1990;1:555-566 |
| Approved | Approved::No |
| Keyword | WBRKeyword::PDGF, WBRKeyword::platelet, WBRKeyword::derived, WBRKeyword::growth, WBRKeyword::factor, WBRKeyword::insulin, WBRKeyword::intrinsic, WBRKeyword::tyrosine, WBRKeyword::kinase, WBRKeyword::pathway, WBRKeyword::signaling, WBRKeyword::hormone, WBRKeyword::effect |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |