**Question:** Which of the following would be least likely seen 14 days after a rat is injected with a drug that kills all of its pancreatic B cells?

A. Increased blood sugar levels
B. Increased insulin production
C. Unchanged blood sugar levels
D. Reduced insulin production

**Core Concept:** Pancreatic B cells, also known as beta cells, are responsible for producing and secreting insulin, which helps regulate blood sugar levels. When these cells are destroyed, the body loses its ability to effectively control blood sugar, leading to hyperglycemia (high blood sugar) or diabetes mellitus.

**Why the Correct Answer is Right:** D. Reduced insulin production is the least likely outcome 14 days after injecting a drug that kills pancreatic B cells. While the initial response would be an increase in blood sugar levels due to reduced insulin production, over time, the pancreas would undergo compensatory mechanisms to maintain glucose homeostasis. This would include the activation of alpha cells in the pancreas, which secrete glucagon, a hormone that raises blood sugar levels. Additionally, peripheral tissues would activate glucose uptake and utilization, further reducing the need for insulin.

**Why Each Wrong Option is Incorrect:**

A. Increased blood sugar levels: This is the immediate response to the destruction of pancreatic B cells, as insulin production is reduced, and the body tries to compensate by increasing glucose production in the liver and enhancing glucose uptake in peripheral tissues.
B. Increased insulin production: As mentioned earlier, the pancreas would undergo compensatory mechanisms to maintain glucose homeostasis. While insulin production might initially seem to increase, it is not a long-term solution. Over time, the body would activate alternative mechanisms to regulate blood sugar levels.
C. Unchanged blood sugar levels: In the absence of insulin production, blood sugar levels would naturally increase due to reduced insulin action. However, the compensatory mechanisms mentioned earlier would be activated, which would further elevate blood sugar levels, making this option incorrect.

**Clinical Pearl:** Diabetes mellitus is a long-term consequence of pancreatic B cell destruction. In the acute phase, blood sugar levels may remain unchanged due to compensatory mechanisms. However, over time, the body's efforts to maintain glucose homeostasis will lead to hyperglycemia (high blood sugar) or diabetes mellitus.